Herb & supplement monograph

Delta-9-tetrahydrocannabinol (thc) Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Delta-9-tetrahydrocannabinol (thc) interacts with medications. The heart of this page is the interaction list — every drug Delta-9-tetrahydrocannabinol (thc) is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Delta-9-tetrahydrocannabinol (thc) is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Delta-9-tetrahydrocannabinol (thc) Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, most Delta-9-tetrahydrocannabinol (thc) drug interactions carry a moderate risk, meaning the combination can matter but is rarely dangerous on its own. None of the listed interactions are rated major, but the majority are moderate, and most rest on lab research or limited human reports rather than strong clinical studies.

Interactions deserving the most attention

The clearest concern is with warfarin, where case reports describe a spike in blood-thinning effect in people using THC, so bleeding risk deserves close attention. THC also adds to drowsiness and impairment when combined with alcohol and other sedating medicines, including sleep aids and barbiturates. There is also human evidence that regular THC use can change how the body responds to anesthesia, sometimes requiring more medication before surgery, and one report links heavy cannabis use to serious bleeding with clot-busting stroke drugs.

What the rest of the list means

The long list of interacting medications looks daunting, but most entries are theoretical. They come from lab findings that THC might affect enzymes and transporters the body uses to clear many drugs, and these predicted effects have not been confirmed as clinically meaningful in people. For most everyday medicines, no harmful interaction has actually been shown.

Check your medications against Delta-9-tetrahydrocannabinol (thc)

Based on HelloPharmacist’s Delta-9-tetrahydrocannabinol (thc) interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Delta-9-tetrahydrocannabinol (thc)

1098 medications have a known interaction with Delta-9-tetrahydrocannabinol (thc), graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
AbametapirXeglyze
Moderate Cytochrome P450 3a4 (cyp3a4) Inhibitors

Theoretically, CYP3A4 inhibitors might increase the levels and clinical effects of THC.

Read the full Delta-9-tetrahydrocannabinol (thc) + Abametapir interaction
AbciximabReoPro
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, THC might increase the risk of bleeding when used concomitantly with anticoagulant/antiplatelet drugs.

Read the full Delta-9-tetrahydrocannabinol (thc) + Abciximab interaction
Abiraterone
Moderate Cytochrome P450 3a4 (cyp3a4) Inhibitors

Theoretically, CYP3A4 inhibitors might increase the levels and clinical effects of THC.

Read the full Delta-9-tetrahydrocannabinol (thc) + Abiraterone interaction Abiraterone drug page: uses, dosage & side effects
AbrocitinibCibinqo
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, THC might increase the risk of bleeding when used concomitantly with anticoagulant/antiplatelet drugs.

Read the full Delta-9-tetrahydrocannabinol (thc) + Abrocitinib interaction Abrocitinib drug page: uses, dosage & side effects
AcalabrutinibCalquence
Moderate P-glycoprotein Substrates

Theoretically, THC might alter levels of drugs that are substrates of P-glycoprotein (P-gp).

Read the full Delta-9-tetrahydrocannabinol (thc) + Acalabrutinib interaction Acalabrutinib drug page: uses, dosage & side effects
AcenocoumarolSintrom
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, THC might increase the risk of bleeding when used concomitantly with anticoagulant/antiplatelet drugs.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acenocoumarol interaction
AcepromazineAtravet
Moderate Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acepromazine interaction
AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen interaction Acetaminophen drug page: uses, dosage & side effects
Acetaminophen, AspirinGemnisyn
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Aspirin interaction
Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, THC might increase the risk of bleeding when used concomitantly with anticoagulant/antiplatelet drugs.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Aspirin, Caffeine interaction
Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Brompheniramine, Phenylpropanolamine interaction
Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Butalbital interaction
Acetaminophen, Butalbital, CaffeineEsgic, Esgic Plus, Fiogesic, Fioricet, Repan, Tecnal +1 more
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Butalbital, Caffeine interaction Acetaminophen, Butalbital, Caffeine drug page: uses, dosage & side effects
Acetaminophen, Butalbital, Caffeine, CodeineEsgic with Codeine, Fioricet w/ Codeine
Moderate Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Butalbital, Caffeine, Codeine interaction
Acetaminophen, Butalbital, CodeineBancap w/ Codeine
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Butalbital, Codeine interaction
Acetaminophen, Butalbital, Codeine PhosphatePhrenilin #3
Moderate Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Butalbital, Codeine Phosphate interaction
Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, PhenylephrineHycomine Compound
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, Phenylephrine interaction
Acetaminophen, Caffeine, CodeineGesic C15, Gesic C30, Gesic C8, Lenoltec 1, Lenoltec 2, Lenoltec 3 +1 more
Moderate Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Codeine interaction
Acetaminophen, Caffeine, Codeine, SalicylamideCodalan No.1, Codalan No.2, Codalan No.3
Moderate Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Codeine, Salicylamide interaction
Acetaminophen, Caffeine, DihydrocodeineDHC Plus, Panlor DC, Panlor SS
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Dihydrocodeine interaction
Acetaminophen, Caffeine, IsomethepteneMigralam
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Isometheptene interaction
Acetaminophen, Caffeine, PyrilamineMidol Max Strength Menstrual
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Caffeine, Pyrilamine interaction
Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan HbrVicks Formula 44M Cough, Cold & Flu Relief
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan Hbr interaction
Acetaminophen, Chlorpheniramine, Codeine, PhenylephrineColrex
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine interaction
Acetaminophen, Chlorpheniramine, DextromethorphanCoricidin II Extra Strength Cold and Flu
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Dextromethorphan interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan HydrobromideCoricidin HBP Maximum Strength Flu
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Dextromethorphan Hydrobromide interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PhenylpropanolamineMulti Symptom Cold Relief
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Dextromethorphan, Phenylpropanolamine interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PseudoephedrineChildren's Tylenol Cold Plus Cough, Tylenol Cold Ex Strength
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Dextromethorphan, Pseudoephedrine interaction
Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, SalicylamideRhinogesic GG
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, Salicylamide interaction
Acetaminophen, Chlorpheniramine, PhenylephrineAlka-Seltzer PLUS, Histex SR, Protid
Moderate Cytochrome P450 2e1 (cyp2e1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.

Read the full Delta-9-tetrahydrocannabinol (thc) + Acetaminophen, Chlorpheniramine, Phenylephrine interaction
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Delta-9-tetrahydrocannabinol (thc) combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Delta-9-tetrahydrocannabinol (thc) affects

Every type of medication (drug category) Delta-9-tetrahydrocannabinol (thc) is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 16 drug categories Delta-9-tetrahydrocannabinol (thc) interacts with
Alcohol (ethanol)AnesthesiaAnticoagulant/antiplatelet DrugsBarbituratesCns DepressantsCytochrome P450 2c9 (cyp2c9) InducersCytochrome P450 2c9 (cyp2c9) InhibitorsCytochrome P450 2e1 (cyp2e1) SubstratesCytochrome P450 3a4 (cyp3a4) InducersCytochrome P450 3a4 (cyp3a4) InhibitorsP-glycoprotein SubstratesTheophyllineThrombolytic DrugsWarfarin (coumadin)Cytochrome P450 2c9 (cyp2c9) SubstratesCytochrome P450 3a4 (cyp3a4) Substrates
Alcohol (Ethanol)

Theoretically, THC might have additive effects when used with alcohol.
THC can have CNS depressant effects. Theoretically, concomitant use of alcohol with THC can have additive effects including psychomotor impairment, sedation, and changes in mood and behavior.

Likelihood Possible Evidence D
Anesthesia

THC use might alter the safety and clinical effects of various forms of anesthesia.
Cannabis contains THC. A small clinical study shows that higher doses of propofol may be needed to achieve relaxation and loss of consciousness in chronic cannabis users compared with nonusers. Another small clinical study shows that use of cannabis within 72 hours prior to undergoing surgery requiring atropine anesthesia may increase the risk of sustained postoperative tachycardia. The exact mechanisms of these interactions are unclear. Obtain a patient's history of cannabis use preoperatively and advise patients to discontinue use for at least 2 weeks prior to undergoing surgery.

Likelihood Possible Evidence B
Anticoagulant/Antiplatelet Drugs

Theoretically, THC might increase the risk of bleeding when used concomitantly with anticoagulant/antiplatelet drugs.
In vitro research shows that THC inhibits platelet aggregation.

Likelihood Possible Evidence D
Barbiturates

Theoretically, THC might increase the levels and adverse effects of barbiturates.
Some research shows that synthetic THC (dronabinol) increases the elimination half-life of pentobarbital by 4 hours when dosed concomitantly. Also, in animal research, THC potentiated pentobarbital-induced sleep by more than three-fold.

Likelihood Possible Evidence D
Cns Depressants

Theoretically, THC might have additive effects if used with other CNS depressants.
Cannabis containing THC can have CNS depressant effects. Combining THC with other CNS depressants might result in additive or synergistic effects.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Inducers

Theoretically, drugs that are CYP2C9 inducers might decrease the levels and clinical effects of THC.
THC is a substrate of CYP2C9 enzymes.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Inhibitors

Theoretically, drugs that are CYP2C9 inhibitors might increase the levels and adverse effects of THC.
THC is a substrate of CYP2C9 enzymes.

Likelihood Possible Evidence D
Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, THC might decrease the levels and clinical effects of CYP2E1 substrates.
In vitro research shows that cannabis containing THC can induce the activity of CYP2E1, which might increase the metabolism of CYP2E1 substrates. It is unclear if this effect is due to THC, other constituents, or the combination.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Inducers

Theoretically, CYP3A4 inducers might reduce the levels and clinical effects of THC.
THC is a substrate of CYP3A4 enzymes.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Inhibitors

Theoretically, CYP3A4 inhibitors might increase the levels and clinical effects of THC.
THC is a substrate of CYP3A4 enzymes.

Likelihood Possible Evidence D
P-Glycoprotein Substrates

Theoretically, THC might alter levels of drugs that are substrates of P-glycoprotein (P-gp).
Most in vitro research suggests that THC can inhibit P-gp and increase the accumulation of probe compounds by reducing P-gp mediated drug efflux. In vitro studies in kidney cell lines show that a 1-hour exposure to CBD and THC inhibits P-gp. THC may also alter the expression of P-gp, although this effect appears to vary based on duration of exposure. Some in vitro research in lymphoblastoid leukemia cell lines indicates that a 1-hour exposure to cannabinoids does not affect P-gp expression, while a prolonged 72-hour exposure decreases P-gp expression. Other in vitro research in these cell lines shows that a 4-hour exposure to THC and CBD induces P-gp gene expression, while exposure for longer than 4 hours and up to 48 hours does not induce P-gp gene expression.

Likelihood Possible Evidence D
Theophylline

Theoretically, THC might reduce the levels and clinical effects of theophylline.
Smoking cannabis containing THC seems to increase the metabolism of theophylline. It is unclear if this effect is due to THC, other constituents, or the combination.

Likelihood Possible Evidence D
Thrombolytic Drugs

THC might augment the effects of thrombolytic drugs and increase the risk of severe bleeding.
Cannabis contains THC. A case of cerebral hemorrhage has been reported for a 51-year-old female and chronic cannabis user who had consumed a large amount of cannabis prior to receiving recombinant tissue plasminogen activator (rtPA) for ischemic stroke. Hemorrhage had been ruled out prior to providing the rtPA. The exact mechanism of this interaction is unclear. It is also unclear if this effect is due to THC, other constituents, or the combination.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Concomitant use with THC seems to increase the levels and clinical effects of warfarin.
In vitro research shows that the cannabinoids THC, cannabidiol (CBD), and cannabinol inhibit the cytochrome P450 2C9 (CYP2C9)-mediated 7-hydroxylation of S-warfarin in a concentration-dependent manner. There are also three case reports of patients chronically taking warfarin that developed a spike in international normalized ratio (INR) after smoking cannabis or taking medical cannabis orally. Although the dose of THC consumed in all cases is unknown, one of the patients doubled the amount of THC consumed from 7.5 mg to 14.7 mg daily for one week.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, THC might increase the levels and adverse effects of CYP2C9 substrates.
In vitro research shows that THC moderately inhibits the CYP2C9-mediated 7-hydroxylation of S-warfarin in a concentration-dependent manner. In vitro research also shows that cannabis extracts containing THC modestly inhibit the CYP2C9 metabolism of tolbutamide; extracts providing the specific cannabinoids cannabidiol (CBD) or cannabigerol (CBG) alone had stronger inhibitory effects than extracts containing both THC and CBD. Theoretically, THC may inhibit the metabolism of other CYP2C9 substrates. Conversely, a crossover clinical study in healthy adults shows that oral THC does not inhibit CYP2C9.

Likelihood Unlikely Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, THC may increase the levels and clinical effects of CYP3A4 substrates.
In vitro research shows that cannabis containing THC might modestly inhibit the activity of CYP3A4 enzymes, which might decrease the metabolism of CYP3A4 substrates. It is unclear if this effect is due to THC, other constituents, or the combination. In vitro research also shows that cannabis extracts containing THC modestly inhibit the CYP3A4 metabolism of testosterone; extracts providing the specific cannabinoids cannabidiol (CBD) or cannabigerol (CBG) alone had stronger inhibitory effects than extracts containing both THC and CBD. Conversely, a crossover clinical study in healthy adults shows that oral THC does not inhibit CYP3A4.

Likelihood Unlikely Evidence D
Monograph

Delta-9-tetrahydrocannabinol (thc): Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

THC is the main mind-altering compound in cannabis and is best known for causing a 'high.' A prescription form (dronabinol) is approved for chemotherapy-related nausea and appetite loss, but for most other uses the evidence is mixed or limited, and THC can impair thinking and driving. It should be avoided in pregnancy and breastfeeding and used only with medical guidance.

Delta-9-tetrahydrocannabinol (thc)
Scientific name
Cannabis sativa
Family
Cannabaceae
Part used
Flowering tops and resin of the cannabis plant (THC is a single cannabinoid isolated or concentrated from these)
Common forms
Prescription oral capsules (dronabinol), oral oil/solution, dried flower, vape and concentrate products (such as butane hash oil/dabs), tinctures, and edibles
People commonly use it for
  • Chronic or nerve pain
  • Nausea and vomiting from chemotherapy
  • Appetite loss and weight loss
  • Muscle spasticity
  • Sleep problems
  • Anxiety and stress

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallUse caution

THC is psychoactive, can impair judgment and coordination, and its legal status varies; use only under medical supervision.

PregnancyUnsafe

When used orally or inhaled. Cannabinoid constituents in cannabis, such as THC, pass through the placenta and can reduce fetal growth and increase the...

Read the full pregnancy detail
BreastfeedingLikely Unsafe

When used orally or inhaled. THC is concentrated and excreted in breast milk for longer than 6 weeks after cessation of use; prolonged use of cannabis...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Delta-9-tetrahydrocannabinol (THC) is the main psychoactive (mind-altering) compound found in the cannabis plant, Cannabis sativa. It is one of more than 80 cannabinoids identified in cannabis. THC is what causes the 'high' that people associate with marijuana.

Cannabis grows in many parts of the world and is cultivated both legally and illegally. THC can be found in dried cannabis flower, in concentrated products such as butane hash oil (also called dabs, budder, or wax), in edibles and tinctures, and in a prescription medicine called dronabinol.

People use THC for both recreational and medical reasons. Medically, it is most often used to ease nausea, improve appetite, and help with pain. Its legal status varies widely from place to place, so it is important to know your local laws.

How it works

THC works mainly by acting on the body's endocannabinoid system. This is a network of receptors (called CB1 and CB2) found in the brain, nerves, and immune system. THC attaches to these receptors, especially CB1 receptors in the brain, which produces its mind-altering and pain-relieving effects.

By acting on these receptors, THC can change how the brain processes pain, mood, appetite, and the sense of nausea. Much of what we understand comes from laboratory and animal research, as well as some human studies.

Because THC affects brain receptors involved in thinking and coordination, it can also impair memory, reaction time, and judgment while it is active in the body.

Effectiveness

Does Delta-9-tetrahydrocannabinol (thc) work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by .

Evidence overview · 18 uses evaluated
18 Insufficient evidence
How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.
2Likely EffectiveGood evidence, though not yet conclusive.
3Possibly EffectiveSome evidence suggests a benefit.
4Possibly IneffectiveSome evidence it may not help.
5Likely IneffectiveFairly strong evidence it doesn’t help.
6IneffectiveStrong evidence it doesn’t work.
7Insufficient Reliable Evidence to RateToo little research to say either way.

For Delta-9-tetrahydrocannabinol (thc), current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 18 conditions — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Alcohol use disorder
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using THC for alcohol use disorder, there is insufficient reliable information about the clinical effects of THC for this purpose.

Insufficient Reliable Evidence To Rate Blepharospasm
Rating & evidence shown verbatim from Natural Medicines

Oral THC has only been evaluated as a component of a cannabis extract; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Cachexia
Rating & evidence shown verbatim from Natural Medicines

Oral THC has only been evaluated as a component of a cannabis extract; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Cancer-related pain
Rating & evidence shown verbatim from Natural Medicines

Non-inhaled THC may be beneficial in patients with cancer-related pain that is not adequately controlled with standard treatment.

Insufficient Reliable Evidence To Rate Chemotherapy-induced nausea and vomiting (CINV)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if a cannabis oromucosal spray or oral cannabis extract, providing standard doses of THC in combination with other ingredients, is beneficial for the prevention of CINV.

Insufficient Reliable Evidence To Rate Crohn disease
Rating & evidence shown verbatim from Natural Medicines

Oral THC has only been evaluated as a component of cannabis products; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Dementia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral THC might reduce neuropsychiatric symptoms of dementia in hospitalized patients.

Insufficient Reliable Evidence To Rate Diabetes
Rating & evidence shown verbatim from Natural Medicines

Sublingual THC has only been evaluated as a component of a cannabis extract; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Fibromyalgia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if inhaled THC in cannabis vapor might reduce fibromyalgia pain.

Insufficient Reliable Evidence To Rate Glaucoma
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oromucosal THC reduces glaucoma risk.

Insufficient Reliable Evidence To Rate HIV/AIDS-related wasting
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral THC attenuates wasting in patients with HIV.

Insufficient Reliable Evidence To Rate Hypertension
Rating & evidence shown verbatim from Natural Medicines

Oral THC has only been evaluated as a component of a cannabis extract; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Insomnia
Rating & evidence shown verbatim from Natural Medicines

Sublingual THC has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Multiple sclerosis (MS)
Rating & evidence shown verbatim from Natural Medicines

A specific cannabis oromucosal spray and oral cannabis extract, providing standard doses of THC in combination with other ingredients, seems to modestly reduce spasticity in patients with MS. The effect of THC alone on symptoms of MS is unclear.

Insufficient Reliable Evidence To Rate Neuropathic pain
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral THC is beneficial for neuropathic pain.

Insufficient Reliable Evidence To Rate Parkinson disease
Rating & evidence shown verbatim from Natural Medicines

Oral THC has only been evaluated as a component of a cannabis extract; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Rheumatoid arthritis (RA)
Rating & evidence shown verbatim from Natural Medicines

It is unclear whether an oromucosal cannabis spray containing THC improves RA symptoms.

Insufficient Reliable Evidence To Rate Ulcerative colitis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if inhaled THC as part of smoked cannabis flower improves symptoms of ulcerative colitis.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

THC is psychoactive and can affect your ability to think clearly, drive, or operate machinery. Do not drive or use heavy equipment while under its effects.

People with a history of psychosis, schizophrenia, bipolar disorder, severe anxiety, or heart disease should be especially cautious, as THC may worsen these conditions. Older adults may be more sensitive to its effects. Regular heavy use can lead to dependence.

Pregnancy: Avoid THC. It crosses the placenta and may affect a baby's brain development and birth outcomes. Breastfeeding: Avoid THC. It passes into breast milk and can affect a nursing infant. Always talk to a pharmacist or doctor before using any THC product, and remember that its legal status differs by location.

Side effects

Common side effects of THC include feeling 'high,' dizziness, drowsiness, dry mouth, red eyes, increased appetite, rapid heartbeat, and changes in mood. Some people feel relaxed, while others feel anxious or paranoid.

Higher doses or strong concentrated products (such as dabs) can cause more intense effects, including confusion, panic, hallucinations, vomiting, and a fast or irregular heartbeat. Long-term heavy use may lead to memory problems, dependence, and a condition that causes severe repeated vomiting (cannabinoid hyperemesis syndrome).

Smoking or vaping cannabis can also irritate the lungs and airways. Seek medical help if you experience chest pain, fainting, severe vomiting, or extreme distress.

Delta-9-tetrahydrocannabinol (thc): Reported Adverse Effects

Documented safety reports on Delta-9-tetrahydrocannabinol (thc) from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

There is limited reliable information available about the adverse effects associated with pure THC. When inhaled or used orally, cannabis can cause various adverse effects, many of which are thought to be related to THC. For more information on cannabis-related adverse effects, see the Cannabis monograph.

Most Common Adverse Effects:

All ROAs: When cannabis containing THC is used, dizziness, dry mouth, fatigue, headache, increased appetite, nausea, paranoid and dissociative thinking, and sedation have occurred. Intoxicating doses can impair declarative memory, motor coordination, reaction time, and visual perception for up to 8 hours. It is unclear if these adverse effects are due to THC, other constituents, or a combination.

Serious Adverse Effects (Rare):

All ROAs: When higher doses of cannabis containing THC are used, acute coronary syndrome, arrhythmias, blood pressure changes, cannabinoid hyperemesis syndrome (CHS), hallucinations, pancreatitis, panic, psychosis, and seizures have occurred. It is unclear if these adverse effects are due to THC, other constituents, or a combination.

Reports by condition
Anxiety Psychiatric

Cannabinoids such as THC can increase anxiety, confusion, depressed mood, and hallucinations, and reduce motivation. Cannabis dabbing, the making of a waxy product with extremely high concentrations of THC, is thought to increase the risk of anxiety, agitation, paranoia, and psychosis. When consumed in large amounts, edible cannabis products containing at least 50 mg of THC have been associated with anxiety, abnormal behavior, psychosis, and suicidal tendencies.

A case of erratic speech and hostile behaviors, followed by suicidal actions resulting in death, has been reported in a 19-year-old male who consumed an edible cannabis cookie. According to the product label, the serving size should have been one-sixth of the cookie, or 10 mg of THC. However, the patient ate the entire cookie after not experiencing effects within 30-60 minutes of the initial dose. Due to this case and other cases of overconsumption of edible cannabis products, in February 2015 the state of Colorado began requiring that edible cannabis products contain no more than 10 mg of THC per serving or that the products have clear demarcation of each 10 mg serving if they contain more than 10 mg of THC.

One small clinical trial shows that inhaling vaporized cannabis containing THC 10 mg, alone or with cannabidiol (CBD) 10-30 mg, modestly induces psychotic symptoms. Also, a single dose of inhaled cannabis providing THC 13.75 mg and < 1% CBD increases feelings of anxiety when compared to cannabis providing CBD 13.75 mg and

  1. Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for medical use: A systematic review and meta-analysis. JAMA. 2015;313(24):2456-73.
  2. Murray CH, Glazer JE, Lee R, Nusslock R, de Wit H. ?9-THC reduces reward-related brain activity in healthy adults. Psychopharmacology (Berl) 2022;239(9):2829-2840.
  3. Pisani S, McGoohan K, Velayudhan L, Bhattacharyya S. Safety and Tolerability of Natural and Synthetic Cannabinoids in Older Adults: A Systematic Review and Meta-Analysis of Open-Label Trials and Observational Studies. Drugs Aging 2021;38(10):887-910.
  4. Mullins MF. Cannabis dabbing: An emerging trend. Nursing. 2021;51(5):46-50.
  5. Hancock-Allen JB, Barker L, VanDyke M, Holmes DB. Notes from the Field: Death Following Ingestion of an Edible Marijuana Product--Colorado, March 2014. MMWR Morb Mortal Wkly Rep. 2015;64(28):771-2.
  6. Monte AA, K Shelton SK, Mills E., Acute Illness Associated With Cannabis Use, by Route of Exposure: An Observational Study. Ann Intern Med. 2019 Apr 16;170(8):531-537.
  7. Englund A, Oliver D, Chesney E, et al. Does cannabidiol make cannabis safer? A randomised, double-blind, cross-over trial of cannabis with four different CBD:THC ratios. Neuropsychopharmacology 2022.
  8. Hutten NRPW, Arkell TR, Vinckenbosch F, et al. Cannabis containing equivalent concentrations of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) induces less state anxiety than THC-dominant cannabis. Psychopharmacology (Berl) 2022;239(11):3731-374
  9. Zamarripa CA, Spindle TR, Surujunarain R, et al. Assessment of orally administered ?9-tetrahydrocannabinol when coadministered with cannabidiol on ?9-tetrahydrocannabinol pharmacokinetics and pharmacodynamics in healthy adults: A randomized clinical trial
  10. Budney AJ, Roffman R, Stephens R, Walker D. Marijuana dependence and its treatment. Addict Sci Clin Pract. 2007;4(1):4-16.
  11. Bahji A, Stephenson C, Tyo R, Hawken ER, Seitz DP. Prevalence of Cannabis Withdrawal Symptoms Among People With Regular or Dependent Use of Cannabinoids: A Systematic Review and Meta-analysis. JAMA Netw Open. 2020;3(4):e202370.
  12. Bonnet U, Preuss UW. The cannabis withdrawal syndrome: current insights. Subst Abuse Rehabil. 2017;8:9-37.
  13. Zehra A, Burns J, Liu CK, et al. Cannabis Addiction and the Brain: a Review. J Neuroimmune Pharmacol. 2018;13(4):438-52.
Arrhythmia Cardiovascular

Orally, edible cannabis products containing 50 mg or more of THC have been associated with myocardial infarction and ventricular arrhythmia. In a case report, a 2-year-old boy developed bradycardia with first-degree atrioventricular block which lasted 12 hours, after accidentally consuming an unknown number of cannabis gummies containing THC. Additionally, taking a prescription drug called dronabinol (Marinol) or nabilone (Cesamet), a synthetic form of THC, has been associated with hypotension, hypertension, syncope and/or tachycardia.

There is case report of pericardial effusion suspected to be related to vaping cannabis 1.5 mg daily, providing 95% THC, for two months. However, the presence of contaminants in the product could not be ruled out. Treatment included aspirin 325 mg every 8 hours, colchicine 0.5 mg every 12 hours, and pantoprazole 40 mg every 12 hours.

A case of ventricular bigeminy and a case of circulatory collapse have been considered to be related to treatment with a specific oromucosal spray that contains THC 2.7 mg and cannabidiol 2.5 mg per actuation (Sativex, GW Pharmaceuticals).

Cannabis containing THC has also been associated with other cardiovascular adverse effects, including increased blood pressure, increased heart rate, arrhythmia, acute coronary syndrome, myocardial infarction, and stroke. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

  1. Monte AA, K Shelton SK, Mills E., Acute Illness Associated With Cannabis Use, by Route of Exposure: An Observational Study. Ann Intern Med. 2019 Apr 16;170(8):531-537.
  2. Idris I, Diez JR, Assoku BA, Beker S. Accidental ingestion of tetrahydrocannabinol-laced gummies causing bradycardia and first-degree atrioventricular block in a pediatric patient: A case report. Cureus 2022;14(7):e26826.
  3. Highlights of prescribing information. MARINOL (dronabinol) capsules, for oral use, CIII. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf. Accessed April 10, 2023.
  4. Cesamet (nabilone) capsules for oral administration. May 2006. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2006/018677s011lbl.pdf. Accessed April 10, 2023.
  5. Maharaj N, Swarath S, Seecheran R, Seecheran V, Seecheran NA. Suspected cannabis vaping-induced pericardial effusion. J Investig Med High Impact Case Rep 2022;10:23247096221140251.
  6. Rog, D. J., Nurmikko, T. J., Friede, T., and Young, C. A. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 9-27-2005;65(6):812-819.
  7. Rog, D. J., Nurmikko, T. J., and Young, C. A. Oromucosal delta9-tetrahydrocannabinol/cannabidiol for neuropathic pain associated with multiple sclerosis: an uncontrolled, open-label, 2-year extension trial. Clin Ther. 2007;29(9):2068-2079.
Cancer Oncologic

There is some concern that use of cannabis containing THC increases the risk for cancer. A meta-analysis of observational case-control studies found that cannabis is not associated with an increased risk for head and neck squamous cell carcinoma or oral cancer. However, more than 10 years of cannabis use is associated with an increased risk for testicular germ cell tumor. It is unclear if this is due to THC, other constituents, or a combination.

  1. Ghasemiesfe M, Barrow B, Leonard S, Keyhani S, Korenstein D. Association between marijuana use and risk of cancer: a systematic review and meta-analysis. JAMA Netw Open. 2019 Nov 1;2(11):e1916318.
Cancer Gastrointestinal

Meta-analyses of clinical and observational research involving adults with a mean age of at least 50 years shows that increasing the dose of natural or synthetic THC in cannabinoid-based medicines is associated with a modest increase in the rate of dry mouth, nausea, and vomiting. Dry mouth has also been reported in clinical research. In addition, taking a prescription drug called dronabinol (Marinol) or nabilone (Cesamet), synthetic forms of THC, has been associated with abdominal pain.

Cannabis oromucosal spray that contains THC 2.7 mg and cannabidiol 2.5 mg per actuation (Sativex, GW Pharmaceuticals) can cause dizziness, dry mouth, nausea, and bad taste. Less commonly, this product may cause red and white buccal mucosal patches to develop inside the mouth.

Cannabis containing THC has been associated with other gastrointestinal adverse effects, including cannabinoid hyperemesis syndrome (CHS). However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph. Taking a prescription drug called nabilone (Cesamet) 2 mg, a synthetic compound similar to THC, for 7 weeks exacerbated nausea and vomiting in a patient with cancer. CHS was suspected. Symptoms did not recur after the nabilone was stopped. The patient had been using nabilone 0.5 mg for 5 years to control neuralgia; however, the dose had been increased to 2 mg to help with cancer pain.

  1. Velayudhan L, McGoohan K, Bhattacharyya S. Safety and tolerability of natural and synthetic cannabinoids in adults aged over 50 years: A systematic review and meta-analysis. PLoS Med. 2021;18(3):e1003524.
  2. Pisani S, McGoohan K, Velayudhan L, Bhattacharyya S. Safety and Tolerability of Natural and Synthetic Cannabinoids in Older Adults: A Systematic Review and Meta-Analysis of Open-Label Trials and Observational Studies. Drugs Aging 2021;38(10):887-910.
  3. Zubcevic K, Petersen M, Bach FW, et al. Oral capsules of tetra-hydro-cannabinol (THC), cannabidiol (CBD) and their combination in peripheral neuropathic pain treatment. Eur J Pain 2022.
  4. Highlights of prescribing information. MARINOL (dronabinol) capsules, for oral use, CIII. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf. Accessed April 10, 2023.
  5. Cesamet (nabilone) capsules for oral administration. May 2006. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2006/018677s011lbl.pdf. Accessed April 10, 2023.
  6. Rog, D. J., Nurmikko, T. J., Friede, T., and Young, C. A. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 9-27-2005;65(6):812-819.
  7. Perras, C. Sativex for the management of multiple sclerosis symptoms. Issues Emerg.Health Technol. 2005;(72):1-4.
  8. Rog, D. J., Nurmikko, T. J., and Young, C. A. Oromucosal delta9-tetrahydrocannabinol/cannabidiol for neuropathic pain associated with multiple sclerosis: an uncontrolled, open-label, 2-year extension trial. Clin Ther. 2007;29(9):2068-2079.
  9. Lynch, M. E. and Campbell, F. Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials. Br.J.Clin.Pharmacol. 2011;72(5):735-744.
  10. Richards, B. L., Whittle, S. L., and Buchbinder, R. Neuromodulators for pain management in rheumatoid arthritis. Cochrane.Database.Syst.Rev. 2012;1:CD008921.
  11. Busse JW, Vankrunkelsven P, Zeng L, et al. Medical cannabis or cannabinoids for chronic pain: a clinical practice guideline. BMJ 2021;374:n2040.
  12. Senderovich H, Waicus S. A case report on cannabinoid hyperemesis syndrome in palliative care: How good intentions can go wrong. Oncol Res Treat 2022;45(7-8):438-443.
Cluster headache Neurologic/CNS

Meta-analyses of clinical and observational research involving adults with a mean age of at least 50 years show that increasing the dose of natural or synthetic THC in cannabinoid-based medicines is associated with a modest increase in overall adverse effects, including dizziness/light-headedness, mobility/balance/coordination difficulties, somnolence, disorientation, memory impairment, fatigue, and euphoria. Euphoria is also reported in clinical research. Cannabis extract oromucosal spray that contains THC 2.7 mg and cannabidiol 2.5 mg per actuation (Sativex, GW Pharmaceuticals) can cause dizziness, lightheadedness, sleepiness, and fatigue.

Intoxicating doses of THC-containing cannabis impair reaction time, motor coordination, declarative memory, and visual perceptions, and can also produce panic reactions and other emotional disturbances. An individual's driving ability can be impaired for up to 8 hours. A small prospective study has found that inhaling vaporized cannabis containing THC 13.75 mg or THC/cannabidiol 13.75 mg increases lane weaving for the first 100 minutes when compared with placebo. This impairment was comparable to that of a blood alcohol concentration of 0.05%, which is considered to indicate clinically relevant impairment. The validity of this finding is limited because the study only tested a single dose of cannabis, which does not mimic typical real-world use. Acute use of cannabis has also been associated with increased motor collision risk, especially if the driver is using alcohol or other drugs concomitantly. Two retrospective studies have found that state-based legalization and commercialization of cannabis is associated with increased traffic fatalities. These studies are limited due to their retrospective nature and a lack of control over other confounding factors such as out-of-state cannabis tourism that could have affected driving fatalities. It is unclear if these adverse effects are due to THC, other constituents, or a combination.

A case of cannabis-induced acute encephalopathy and severe dehydration is reported in a 94-year-old woman given cannabis by a family member. The product had been marketed as pure cannabidiol (CBD); however, a urinary analysis resulted positive for THC. The patient was hospitalized, received supportive care, and was discharged after 6 days with complete resolution of cognitive symptoms. Additionally, 2 cases of recurrent reversible cerebral vasoconstriction requiring hospitalization and escalated care are reported in adults. Both cases involved the use of THC, history of hypertension, and presentations that included thunderclap headaches and stroke, one ischemic and the other hemorrhagic, adding further complexity to their cases that only resulted in partial recovery. However, the role of THC in these cases is not well understood.

Some evidence shows that the adverse effects of THC may be increased when consumed with large amounts of CBD. A small study in healthy adults shows that consumption of brownies containing CBD 640 mg plus THC 20 mg increases feelings of sedation and memory impairment when compared with brownies containing only THC 20 mg.

Cannabis containing THC has also been associated with other neurologic adverse effects, including headache, disorientation, cognitive impairment, and fatigue. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

  1. Velayudhan L, McGoohan K, Bhattacharyya S. Safety and tolerability of natural and synthetic cannabinoids in adults aged over 50 years: A systematic review and meta-analysis. PLoS Med. 2021;18(3):e1003524.
  2. Pisani S, McGoohan K, Velayudhan L, Bhattacharyya S. Safety and Tolerability of Natural and Synthetic Cannabinoids in Older Adults: A Systematic Review and Meta-Analysis of Open-Label Trials and Observational Studies. Drugs Aging 2021;38(10):887-910.
  3. Zubcevic K, Petersen M, Bach FW, et al. Oral capsules of tetra-hydro-cannabinol (THC), cannabidiol (CBD) and their combination in peripheral neuropathic pain treatment. Eur J Pain 2022.
  4. Rog, D. J., Nurmikko, T. J., Friede, T., and Young, C. A. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 9-27-2005;65(6):812-819.
  5. Perras, C. Sativex for the management of multiple sclerosis symptoms. Issues Emerg.Health Technol. 2005;(72):1-4.
  6. Rog, D. J., Nurmikko, T. J., and Young, C. A. Oromucosal delta9-tetrahydrocannabinol/cannabidiol for neuropathic pain associated with multiple sclerosis: an uncontrolled, open-label, 2-year extension trial. Clin Ther. 2007;29(9):2068-2079.
  7. Lynch, M. E. and Campbell, F. Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials. Br.J.Clin.Pharmacol. 2011;72(5):735-744.
  8. Richards, B. L., Whittle, S. L., and Buchbinder, R. Neuromodulators for pain management in rheumatoid arthritis. Cochrane.Database.Syst.Rev. 2012;1:CD008921.
  9. Duran M, Pérez E, Abanades S, et al. Preliminary efficacy and safety of an oromucosal standardized cannabis extract in chemotherapy-induced nausea and vomiting. Br J Clin Pharmacol. 2010;70(5):656-63.
  10. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  11. Kloft L, Otgaar H, Blokland A, Garbaciak A, Monds LA, Ramaekers JG. False memory formation in cannabis users: a field study. Psychopharmacology (Berl). 2019;236(12):3439-3450.
  12. Arkell TR, Vinckenbosch F, Kevin RC, Theunissen EL, McGregor IS, Ramaekers JG. Effect of Cannabidiol and ?9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical Trial. JAMA. 2020;324(21):2177-2186.
  13. Cole TB, Saitz R. Cannabis and Impaired Driving. JAMA. 2020;324(21):2163-2164.
  14. Asbridge, M., Hayden, J. A., and Cartwright, J. L. Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis. BMJ 2012;344:e536.
  15. Li, M. C., Brady, J. E., DiMaggio, C. J., Lusardi, A. R., Tzong, K. Y., and Li, G. Marijuana use and motor vehicle crashes. Epidemiol.Rev. 2012;34(1):65-72.
  16. Rosekind MR, Ehsani JP, Michael JP. Reducing Impaired Driving Fatalities: Data Need to Drive Testing, Enforcement, and Policy. JAMA Intern Med. 2020.
  17. Santaella-Tenorio J, Wheeler-Martin K, DiMaggio CJ, et al. Association of Recreational Cannabis Laws in Colorado and Washington State With Changes in Traffic Fatalities, 2005-2017. JAMA Intern Med. 2020.
  18. Kamer RS, Warshafsky S, Kamer GC. Change in Traffic Fatality Rates in the First 4 States to Legalize Recreational Marijuana. JAMA Intern Med. 2020.
  19. Moussa MK, Hall MAK, Akwe J. Cannabis-induced acute encephalopathy in a 94-year-old woman due to family administration of cannabidiol (CBD) products: A case report. Cureus 2023;15(4):e37927.
  20. Patel PA, Sanborn E, Then R, Williams DM. Recurrent Reversible Cerebral Vasoconstriction Syndrome: A Report of Two Cases. Cureus 2023;15(8):e42992.
  21. Zamarripa CA, Spindle TR, Surujunarain R, et al. Assessment of orally administered ?9-tetrahydrocannabinol when coadministered with cannabidiol on ?9-tetrahydrocannabinol pharmacokinetics and pharmacodynamics in healthy adults: A randomized clinical trial
Diarrhea Renal

A case of acute kidney injury has been reported in a 94-year-old adult after consumption of cannabis containing THC; it was likely caused by pre-existing mild dehydration related to a lack of fluid intake, followed by cannabis-induced diarrhea.

  1. Moussa MK, Hall MAK, Akwe J. Cannabis-induced acute encephalopathy in a 94-year-old woman due to family administration of cannabidiol (CBD) products: A case report. Cureus 2023;15(4):e37927.
Dry eye Ocular/Otic

A meta-analysis of clinical research involving adults with a mean age of at least 50 years shows that increasing the dose of natural or synthetic THC in cannabinoid-based medicines is associated with a modest increase in overall adverse effects, including visual symptoms.

Cannabis containing THC has been associated with other ocular or otic adverse effects, including dry eye, reddening of the eyes, and tinnitus. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

  1. Velayudhan L, McGoohan K, Bhattacharyya S. Safety and tolerability of natural and synthetic cannabinoids in adults aged over 50 years: A systematic review and meta-analysis. PLoS Med. 2021;18(3):e1003524.
Erectile dysfunction (ED) Genitourinary

A meta-analysis of clinical research involving adults with a mean age of at least 50 years shows that increasing the dose of natural or synthetic THC in cannabinoid-based medicines is associated with a modest increase in the rate of male impotence.

Cannabis containing THC has been associated with other genitourinary adverse effects, including priapism and abnormal menstruation. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

  1. Velayudhan L, McGoohan K, Bhattacharyya S. Safety and tolerability of natural and synthetic cannabinoids in adults aged over 50 years: A systematic review and meta-analysis. PLoS Med. 2021;18(3):e1003524.
Erythema Dermatologic

Cannabis containing THC has been associated with dermatologic adverse effects, including erythema multiforme-like recurrent drug eruption. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

Taking a prescription drug called dronabinol (Marinol), a synthetic form of THC, has been associated with hypersensitivity reactions, including skin hives, rash, or flushing.

  1. Highlights of prescribing information. MARINOL (dronabinol) capsules, for oral use, CIII. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf. Accessed April 10, 2023.
Myasthenia gravis Pulmonary/Respiratory

Using a specific oromucosal spray that contains THC 2.7 mg and cannabidiol 2.5 mg per actuation (Sativex, GW Pharmaceuticals) may cause pharyngitis, hoarseness, and throat irritation.

  1. Rog, D. J., Nurmikko, T. J., Friede, T., and Young, C. A. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 9-27-2005;65(6):812-819.
Pancreatitis Endocrine

Cannabis containing THC has been associated with endocrine adverse effects, including weight gain, worsened glycemic control, and acute pancreatitis. However, it is unclear if these adverse effects are due to the THC constituent of cannabis, other constituents, or a combination. For more information on cannabis-related adverse effects, see the Cannabis monograph.

Urinary tract infections (UTIs) Immunologic

Taking a prescription drug called dronabinol (Marinol), a synthetic form of THC, has been associated with hypersensitivity reactions, including lip swelling and oral lesions, skin hives, rash, or flushing, or throat tightness. A meta-analysis of lower quality clinical and observational research suggests that the use of natural or synthetic THC in cannabinoid-based medicines is associated with a slight increase in respiratory and urinary tract infections.

  1. Highlights of prescribing information. MARINOL (dronabinol) capsules, for oral use, CIII. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf. Accessed April 10, 2023.
  2. Pisani S, McGoohan K, Velayudhan L, Bhattacharyya S. Safety and Tolerability of Natural and Synthetic Cannabinoids in Older Adults: A Systematic Review and Meta-Analysis of Open-Label Trials and Observational Studies. Drugs Aging 2021;38(10):887-910.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no single standard dose of THC for general use, and the right amount varies widely from person to person based on tolerance, the product, and the reason for use. Concentrated products contain much more THC than dried flower, which makes accidental overuse easy.

For prescription products such as dronabinol, a doctor sets the dose. For other products, follow the label and start with the lowest amount, especially if you are new to THC, since effects from edibles can take hours to appear.

Always check with a pharmacist or doctor before using THC, particularly if you take other medicines or have health conditions.

Pregnancy & Breastfeeding

Delta-9-tetrahydrocannabinol (thc) & Pregnancy

Unsafe

When used orally or inhaled. Cannabinoid constituents in cannabis, such as THC, pass through the placenta and can reduce fetal growth and increase the risk for preterm birth. Cannabis use during pregnancy is also associated with placental abruption, stillbirth, preterm delivery, fetal abnormalities, low birth weight, small for gestational age, increased need for neonatal intensive care, and childhood leukemia. Prenatal cannabis use has also been associated with long-term adverse developmental effects in the offspring, such as worsened cognition, increased risk for neurodevelopmental disorders such as autism spectrum disorder, and increased risk for psychological issues during adolescence. Due to the observational nature of these studies, it is unclear if cannabis causes these adverse effects. Umbilical artery Doppler scans also show that cannabis use can increase placental vascular resistance. Cannabis use during pregnancy has been associated with increased risk of anemia and hypertension in the mother. Although the safety of pure THC has not been investigated during pregnancy, it is likely that THC is at least partially responsible for these safety concerns. The rate of negative fetal outcomes due to cannabis use during pregnancy may have been previously underestimated due to reliance on maternal self-reporting of use. Recent programs requiring maternal urine toxicology testing have increased awareness of maternal cannabis use and suggest that negative fetal outcomes occur more frequently than previously recorded.

  1. Corsi DJ, Walsh L, Weiss D, et al. Association Between Self-reported Prenatal Cannabis Use and Maternal, Perinatal, and Neonatal Outcomes. JAMA. 2019 Jul 9;322(2):145-152.
  2. Rodriguez CE, Sheeder J, Allshouse AA, et al. Marijuana use in young mothers and adverse pregnancy outcomes: a retrospective cohort study. BJOG. 2019 Nov;126(12):1491-1497.
  3. Paul SP, Hatoum AS, Fine JD, et al. Associations between prenatal cannabis exposure and childhood outcomes: results from the ABCD Study. JAMA Psychiatry. 2020;e202902.
  4. Grzeskowiak LE, Grieger JA, Andraweera P, et al. The deleterious effects of cannabis during pregnancy on neonatal outcomes. Med J Aust. 2020;212(11):519-524.
  5. Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
  6. Johnson, E. M. Substance abuse and women's health. Public Health Rep. 1987;102(4 Suppl):42-48.
  7. Reece, A. S. Chronic toxicology of cannabis. Clin Toxicol.(Phila) 2009;47(6):517-524.
  8. Gunn JK, Rosales CB, Center KE, et al. Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016;6(4):e009986.
  9. Brar BK, Patil PS, Jackson DN, Gardner MO, Alexander JM, Doyle NM. Effect of intrauterine marijuana exposure on fetal growth patterns and placental vascular resistance. J Matern Fetal Neonatal Med. 2019 Nov 11:1-5.
  10. Marchand G, Masoud AT, Govindan M, et al. Birth Outcomes of Neonates Exposed to Marijuana in Utero: A Systematic Review and Meta-analysis. JAMA Netw Open 2022;5(1):e2145653.
  11. Corsi DJ, Donelle J, Sucha E, et al. Maternal cannabis use in pregnancy and child neurodevelopmental outcomes. Nat Med. 2020;26(10):1536-1540.
  12. Smid MC. Marijuana use among young pregnant women: more common and more harmful than we think. BJOG. 2019 Nov;126(12):1498.

Delta-9-tetrahydrocannabinol (thc) & Breastfeeding

Likely Unsafe

When used orally or inhaled. THC is concentrated and excreted in breast milk for longer than 6 weeks after cessation of use; prolonged use of cannabis containing THC during lactation has been associated with delayed motor development. Observational research in mothers who successfully abstained from cannabis use for 6 weeks (confirmed by a negative THC urine screen) after smoking cannabis prenatally at least twice weekly, found that THC levels in breastmilk increased during the first 2 weeks of abstinence and then decreased but remained detectable at 6 weeks. For patients planning to breastfeed, recommend abstaining from THC use prenatally and during lactation. Recommendations to discard breastmilk until THC levels are undetectable are not practical, as this may take more than 6 weeks.

  1. Hebel SK, ed. Drug Facts and Comparisons. 52nd ed. St. Louis: Facts and Comparisons, 1998.
  2. Tyrey L. Delta 9-Tetrahydrocannabinol: a potent inhibitor of episodic luteinizing hormone secretion. J Pharmacol Exp Ther 1980;213:306-8.
  3. Wymore EM, Palmer C, Wang GS, et al. Persistence of ?-9-Tetrahydrocannabinol in Human Breast Milk JAMA Pediatr. 2021. doi: 10.1001/jamapediatrics.2020.6098.
  4. Astley, S. J. and Little, R. E. Maternal marijuana use during lactation and infant development at one year. Neurotoxicol.Teratol. 1990;12(2):161-168.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 76 references that drive our Delta-9-tetrahydrocannabinol (thc) monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  2. Hebel SK, ed. Drug Facts and Comparisons. 52nd ed. St. Louis: Facts and Comparisons, 1998.
  3. Tyrey L. Delta 9-Tetrahydrocannabinol: a potent inhibitor of episodic luteinizing hormone secretion. J Pharmacol Exp Ther 1980;213:306-8. DOI
  4. Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
  5. Marinol Prescribing Information. Solvay Pharmaceuticals, Rev March 2008. Available at: http://www.solvaypharmaceuticals-us.com/static/wma/pdf/1/3/2/5/0/004InsertText500012RevMar2008.pdf (Accessed 2 July 2009).
  6. Yamreudeewong W, Wong HK, Brausch LM, Pulley KR. Probable interaction between warfarin and marijuana smoking. Ann Pharmacother 2009;43:1347-53. PubMed
  7. Pellinen, P., Honkakoski, P., Stenback, F., Niemitz, M., Alhava, E., Pelkonen, O., Lang, M. A., and Pasanen, M. Cocaine N-demethylation and the metabolism-related hepatotoxicity can be prevented by cytochrome P450 3A inhibitors. Eur.J Pharmacol 1-3-1994;2 PubMed
  8. Johnson, E. M. Substance abuse and women's health. Public Health Rep. 1987;102(4 Suppl):42-48.
  9. Astley, S. J. and Little, R. E. Maternal marijuana use during lactation and infant development at one year. Neurotoxicol.Teratol. 1990;12(2):161-168. PubMed
  10. Levy, R., Schurr, A., Nathan, I., Dvilanski, A., and Livne, A. Impairment of ADP-induced platelet aggregation by hashish components. Thromb.Haemost. 12-31-1976;36(3):634-640. DOI
  11. Sheweita, S. A. Narcotic drugs change the expression of cytochrome P450 2E1 and 2C6 and other activities of carcinogen-metabolizing enzymes in the liver of male mice. Toxicology 9-30-2003;191(2-3):133-142. PubMed
  12. Rog, D. J., Nurmikko, T. J., Friede, T., and Young, C. A. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 9-27-2005;65(6):812-819. PubMed
  13. Perras, C. Sativex for the management of multiple sclerosis symptoms. Issues Emerg.Health Technol. 2005;(72):1-4.
  14. Zhu, H. J., Wang, J. S., Markowitz, J. S., Donovan, J. L., Gibson, B. B., Gefroh, H. A., and Devane, C. L. Characterization of P-glycoprotein inhibition by major cannabinoids from marijuana. J Pharmacol Exp.Ther. 2006;317(2):850-857. PubMed
  15. Holland, M. L., Panetta, J. A., Hoskins, J. M., Bebawy, M., Roufogalis, B. D., Allen, J. D., and Arnold, J. C. The effects of cannabinoids on P-glycoprotein transport and expression in multidrug resistant cells. Biochem.Pharmacol 4-14-2006;71(8):1146-115 PubMed
Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Pharmacist Counseling Corner

Delta-9-tetrahydrocannabinol (thc): Common Questions

What is Delta-9-tetrahydrocannabinol (thc) used for, and does it work?
People use Delta-9-tetrahydrocannabinol (thc) for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.
Does Delta-9-tetrahydrocannabinol (thc) interact with prescription medications?
Yes. We list 1098 medications with a known interaction with Delta-9-tetrahydrocannabinol (thc). Use the checker above to see how Delta-9-tetrahydrocannabinol (thc) interacts with a specific drug.
How are Delta-9-tetrahydrocannabinol (thc) interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Delta-9-tetrahydrocannabinol (thc) with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Delta-9-tetrahydrocannabinol (thc) interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
What is THC used for?
THC is best known for the 'high' it causes, but it is also used medically for chemotherapy-related nausea, appetite loss, and sometimes for pain or muscle spasms. A prescription form called dronabinol is approved for some of these uses.
Will THC make me feel high?
Yes. THC is the main psychoactive compound in cannabis and typically causes a high, along with changes in mood, perception, and coordination. The effect depends on the dose and the product.
Is THC safe to use during pregnancy or breastfeeding?
No. THC crosses the placenta and passes into breast milk, and it may harm a baby's brain development. It should be avoided during both pregnancy and breastfeeding.
Can THC be addictive?
Yes. Regular or heavy use of THC can lead to dependence, and some people develop withdrawal symptoms when they stop. Starting low and using it only as needed lowers this risk.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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