Drug & supplement interaction

Cannabis + Fluoxetine

Fluoxetine brand names: Prozac, Sarafem.

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

Fluoxetine falls into 3 drug categories that Cannabis can interact with; the most serious is rated moderate. Theoretically, drugs that are CYP2C9 inhibitors might increase the adverse effects of cannabis.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Cannabis and Fluoxetine

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Cannabis interacts with whole categories of medication. Fluoxetine falls into 3 of those categories, so it can interact with Cannabis in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2C9 (CYP2C9) INHIBITORS

1 of 3

Why this applies to Fluoxetine

Fluoxetine falls under CYTOCHROME P450 2C9 (CYP2C9) INHIBITORS — the group Cannabis interacts with.

Theoretically, drugs that are CYP2C9 inhibitors might increase the adverse effects of cannabis.
Delta-9-tetrahydrocannabinol (THC), an active constituent of cannabis, is a substrate of CYP2C9 enzymes.
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 gist for Prozac (fluoxetine) and cannabis. Your liver uses an enzyme called CYP2C9 to help break down THC, the part of cannabis that gets you high. Fluoxetine can gently block that same enzyme. The concern is that with this pathway slowed, THC may hang around longer and feel stronger, so you could notice more of cannabis's usual effects like drowsiness, dizziness, a racing heart, anxiety, or feeling more impaired than expected.

I'll be honest with you though: this is a theoretical concern based on how the drugs work on paper, not on solid real-world studies. To be clear, fluoxetine is not a prodrug here, and it's the cannabis side that may build up, not the Prozac. If you use both, start low, go slow, and check in with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Product information for Marinol. AbbVie. North Chicago, IL 60064. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS

2 of 3

Fluoxetine also falls under CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS.

Theoretically, CYP3A4 inhibitors might increase the levels and adverse effects of cannabis.
Delta-9-tetrahydrocannabinol (THC), an active constituent of cannabis, is a substrate of CYP3A4 enzymes.
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 gist for this pairing: fluoxetine (Prozac) blocks an enzyme called CYP3A4, and your body uses that same enzyme to clear THC, the part of cannabis that gets you high. So when the two are combined, THC can hang around longer and build up a bit. That means the cannabis effects (feeling stoned, dizziness, a racing heart, drowsiness, or anxiety) could feel stronger or last longer than you'd expect.

I want to be honest about the evidence, though. This is a theoretical concern based on how the enzyme works, not something proven in studies, and it's rated moderate. Fluoxetine isn't a prodrug here, so the direction is straightforward: more THC effect, not less. If you use cannabis and take fluoxetine, just mention it to your pharmacist or doctor so they can keep an eye on you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Product information for Marinol. AbbVie. North Chicago, IL 60064. August 2017. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018651s029lbl.pdf.
Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

3 of 3

Fluoxetine also falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES.

Theoretically, cannabis might increase the levels and adverse effects of CYP2C9 substrates.
In vitro research shows that the cannabis constituents delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol moderately inhibit the CYP2C9-mediated 7-hydroxylation of S-warfarin in a concentration-dependent manner. In vitro research also shows that cannabis extracts modestly inhibit the CYP2C9 metabolism of tolbutamide; extracts providing the specific cannabinoids CBD and cannabigerol (CBG) had stronger inhibitory effects than extracts containing THC and CBD.
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 gist for Prozac (fluoxetine). Cannabis compounds like THC and CBD can slow down a liver enzyme called CYP2C9, which is one of the routes your body uses to break down fluoxetine. If that pathway gets blocked, a bit more of the drug could linger in your system, which in theory could nudge up its effects and side effects (think nausea, headache, jitteriness, trouble sleeping, or feeling more activated).

I want to be honest about how soft this evidence is: it comes from lab dish studies, not real people taking both together. So this is more of a theoretical heads-up than a proven problem. Still, since both can affect mood and alertness, it's worth a quick chat with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Damkier P, Lassen D, Christensen MMH, Madsen KG, Hellfritzsch M, Pottegård A. Interaction between warfarin and cannabis. Basic Clin Pharmacol Toxicol. 2019;124(1):28-31. PubMed
  2. Treyer A, Reinhardt JK, Eigenmann DE, Oufir M, Hamburger M. Phytochemical comparison of medicinal cannabis extracts and study of their CYP-mediated interactions with coumarinic oral anticoagulants. Med Cannabis Cannabinoids. 2023;6(1):21-31. 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 Fluoxetine 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. Fluoxetine)
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 Fluoxetine

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 Fluoxetine, 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 Fluoxetine

This page covers Cannabis only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fluoxetine page lists 163 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 8 major · 127 moderate · 28 minor.

From our pharmacist’s overview on the Fluoxetine page

“Grapefruit is the surprise at the top of fluoxetine's (Prozac) supplement list. In large amounts it can stretch the QT interval, the electrical pause between heartbeats, and fluoxetine, a widely prescribed antidepressant, can do the same, raising the odds of a dangerous rhythm.”

Reviewed by 2 · Jul 18, 2026

Open the Fluoxetine 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 Fluoxetine 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 Fluoxetine 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%

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

29 days ago today
Medication Fluoxetine
Top 1%

#29 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 Fluoxetine

What Is Fluoxetine Used For?

Brand names: Prozac, Sarafem

Fluoxetine is approved to treat four conditions: major depressive disorder (MDD), obsessive-compulsive disorder (OCD), bulimia nervosa (a binge-eating and purging disorder), and panic disorder — with or without agoraphobia (fear of situations that feel hard to escape).

It works for adults across all four conditions, and for children and teens with depression (ages 8–18) and OCD (ages 7–17).

See full Fluoxetine 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 Fluoxetine, 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 Fluoxetine supplement interactions › Every supplement checked against Fluoxetine, ranked by severity Fluoxetine 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 Fluoxetine Together: Common Questions

Can you take Cannabis with Fluoxetine?
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 3 interactions listed for Cannabis and Fluoxetine?
Fluoxetine 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 Fluoxetine 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 Fluoxetine 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.