Drug & supplement interaction

Cannabis + Chlorpromazine

Chlorpromazine brand names: Thorazine, Thorazine Spansules.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Chlorpromazine falls into 2 drug categories that Cannabis can interact with; the most serious is rated moderate. Theoretically, cannabis might have additive effects if used with other CNS depressants.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Cannabis and Chlorpromazine

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Cannabis interacts with whole categories of medication. Chlorpromazine falls into 2 of those categories, so it can interact with Cannabis in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CNS DEPRESSANTS

1 of 2

Why this applies to Chlorpromazine

Chlorpromazine falls under CNS DEPRESSANTS — the group Cannabis interacts with.

Theoretically, cannabis might have additive effects if used with other CNS depressants.
Cannabis can have CNS depressant effects. Combining cannabis with other CNS depressants might result in additive or synergistic effects. A small clinical trial in healthy adults shows that inhaling a high-grade cannabis (Bedrocan International B.V., Veendam, The Netherlands) 100 mg, containing delta-9-tetrahydrocannabinol 21.8% and cannabinol 0.1%, modestly increases subjective feelings of sedation when compared with cannabis alone.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: both cannabis and chlorpromazine (Thorazine) can slow down your brain and nervous system. Chlorpromazine already tends to make people feel drowsy, foggy, or dizzy, and it can lower blood pressure so you feel lightheaded when you stand up. Cannabis can add to that, so together you may feel more sedated, sleepier, or less steady on your feet than with either one alone.

This concern is theoretical, based on how the two work rather than strong studies, so it doesn't mean trouble is guaranteed. Still, it's worth respecting. If you take chlorpromazine and are thinking about cannabis, please check with your doctor or pharmacist first, and don't drive until you know how the combination affects you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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).
  2. Hollister, L. E. Interactions of cannabis with other drugs in man. NIDA Res.Monogr 1986;68:110-116. DOI
  3. van Dam CJ, van der Schrier R, van Velzen M, et al. Inhaled Delta(9)-tetrahydrocannabinol does not enhance oxycodone-induced respiratory depression: randomised controlled trial in healthy volunteers. Br J Anaesth 2023;130(4):485-493.
Minor

ANTIPSYCHOTIC DRUGS

2 of 2

Chlorpromazine also falls under ANTIPSYCHOTIC DRUGS.

Cannabis does not seem to affect blood levels or effects of some antipsychotic drugs.
Human research shows that cannabis use does not affect blood levels or clinical effects of amisulpride, aripiprazole, or olanzapine in patients with schizophrenia and related disorders.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the reassuring part: when researchers looked at cannabis alongside antipsychotics, they didn't see it meaningfully change the blood levels or the effects of those medicines. That study looked at drugs like olanzapine and aripiprazole rather than chlorpromazine specifically, but the takeaway points the same direction, and we'd rate this as a minor, unlikely concern.

The bigger thing to keep in mind isn't a blood-level change, it's overlap in how you feel. Both cannabis and chlorpromazine (Thorazine) can make you drowsy, foggy, dizzy, or lightheaded when you stand up. Stacked together, that sedation and impairment can add up. Cannabis can also stir up anxiety or odd thinking, which isn't ideal when you're being treated for a psychotic condition. Please loop in your doctor or pharmacist before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Alisauskiene R, Johnsen E, Gjestad R, et al. Does drug use affect the efficacy of amisulpride, aripiprazole and olanzapine in patients with schizophrenia spectrum disorders? Results from a pragmatic, randomised study. Gen Hosp Psychiatry 2023;83:185-193. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Cannabis Also Interacts With Other Medications

Cannabis has 2 major, 1,108 moderate, 25 minor known drug interactions in our database — the Chlorpromazine one above is among them. If you take anything else, check it against the full list below.

Major 2 Moderate 1,108 Minor 25 No known interaction 1,695 (incl. Chlorpromazine)
Taking anything else?

Check Another of Your Medications Against Cannabis

Covers the 2,830 medications we’ve checked against Cannabis. Pick one to open its full report.

From our Q&A

Questions About Cannabis or Chlorpromazine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Cannabis or Chlorpromazine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Chlorpromazine

This page covers Cannabis only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chlorpromazine page lists 211 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), American Hellebore (major), Arsenic (major) and Beer (major).

By severity: 17 major · 159 moderate · 35 minor.

Open the Chlorpromazine interaction page

One more smart check

Taking Cannabis as Part of a Dietary Supplement Product? Check It for Interactions

We hold 21 real supplement products containing Cannabis, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cannabis. Your product may carry other ingredients that interact with Chlorpromazine too, on top of Cannabis — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Cannabis and Chlorpromazine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Cannabis
Top 25%

#231 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Chlorpromazine
Steady interest

#1,858 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Cannabis

What is Cannabis?

Cannabis
  • Chronic pain
  • Nausea and vomiting from chemotherapy
  • Muscle spasticity (e.g., multiple sclerosis)
  • Anxiety and stress
  • Sleep problems
  • Appetite stimulation

Cannabis contains many active compounds, mainly THC (which causes a 'high') and CBD (which does not). Some uses, such as chemotherapy-related nausea, certain seizure disorders, and muscle spasticity, have meaningful evidence, while many other popular uses are not well proven. It can cause real side effects and impairment, so talk to your doctor or pharmacist and follow your local laws before using it.

Read the full Cannabis monograph & all interactions
Medication

About Chlorpromazine

What Is Chlorpromazine Used For?

Brand names: Thorazine, Thorazine Spansules

Chlorpromazine is used to manage psychotic disorders and treat schizophrenia. It also controls nausea and vomiting, relieves restlessness and apprehension before surgery, and controls the manic phase of manic-depressive illness. Other uses include relief of intractable hiccups, treatment of acute intermittent porphyria, and use as an adjunct in tetanus treatment.

In children ages 1 to 12, it is used for severe behavioral problems marked by explosive or combative behavior, and for short-term treatment of hyperactive children with conduct disorders. The oral forms are also approved for the management of manifestations of psychotic disorders broadly, in addition to the uses shared with the injection form.

See full Chlorpromazine drug information
Keep checking

Other Drugs & Cannabis

Browse every other medication we’ve checked against Cannabis — both the ones with a known interaction and the ones without. Select any drug for the full detail.

2Major
1,108Moderate
25Minor
1,694No known interaction
2 Major 1,108 Moderate 25 Minor 1,694 No interaction
Major

2 interactions

Moderate

1,108 interactions

Showing 60 of 1,108 moderate interactions — see all 1,108 on the Cannabis page.

Minor

25 interactions

No interaction 1,694 drugs checked — show the list

We also checked Cannabis against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,694 medications checked with no known interaction — see the full Cannabis list.

See the full Cannabis interactions page
See every supplement checked against Chlorpromazine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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

Keep exploring
Cannabis monograph › Uses, safety, and every drug interaction in one place Chlorpromazine supplement interactions › Every supplement checked against Chlorpromazine, ranked by severity Chlorpromazine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Cannabis and Chlorpromazine Together: Common Questions

Can you take Cannabis with Chlorpromazine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Cannabis and Chlorpromazine?
Chlorpromazine belongs to more than one drug category, and Cannabis interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Cannabis and Chlorpromazine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Chlorpromazine and Cannabis?

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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.