How Cannabis Interacts with Drugs
Our tracker shows what is documented on FDA labels, published studies, and what is only predicted based on how the enzymes work scientifically. Use the filters or the search bar for easier access.
This is educational, not medical advice. Do not start, stop, or change any medication based on this page. Absence from this list does not mean an interaction is impossible, and cannabis products vary widely in what they actually contain. Talk to your prescriber or pharmacist.
Clobazam
OnfiCBD raises the active metabolite N-desmethylclobazam roughly threefold.
What to do: Watch for sedation. A clobazam dose reduction is commonly needed.
Source: FDA Epidiolex label, section 7.2Valproate
Depakote, divalproexTaking the two together raises the rate of liver enzyme elevations.
What to do: Check liver function before starting and during treatment.
Source: FDA Epidiolex label, section 5.1, and the divalproex labelsTacrolimus
PrografTacrolimus exposure rises when taken with CBD.
What to do: The label calls for drug level monitoring and considering a dose reduction.
Source: FDA tacrolimus extended-release label, section 7.2Everolimus
AfinitorEverolimus exposure rises when taken with CBD oral solution.
What to do: The label directs a dose reduction.
Source: FDA everolimus label, sections 2.11 and 7.1Sirolimus
RapamuneSirolimus concentrations can rise with concomitant CBD.
What to do: Monitor drug levels.
Source: FDA Epidiolex label, section 7Rifampin
RifadinRifampin lowered CBD exposure by about 32%, so the CBD works less well.
What to do: The label suggests considering up to a twofold CBD dose increase.
Source: FDA Epidiolex label, section 7.1Caffeine
CBD weakly inhibits CYP1A2, so caffeine clears more slowly.
What to do: Usually minor. Consider it if jitteriness or insomnia is new.
Source: FDA Epidiolex label, section 7.2Theophylline
Levels may rise through weak CYP1A2 inhibition.
What to do: Theophylline has a narrow safe range, so monitor levels.
Source: FDA Epidiolex label, section 7.2Tamoxifen
NolvadexChronic low-dose CBD reduced endoxifen, the metabolite that does the work. Less active drug, not more.
What to do: Clinically important in breast cancer treatment. Discuss before combining.
Source: Reduction in tamoxifen metabolites with chronic low-dose CBD · PMID 33191836Fluoxetine
ProzacA reported drug-gene-drug interaction: CBD plus fluoxetine in a CYP2D6 poor metaboliser.
What to do: Relevant if CYP2D6 genotype is known or side effects are unexplained.
Source: A potential drug-gene-drug interaction between cannabidiol, CYP2D6*4 and fluoxetine · PMID 35652796Clozapine
ClozarilSmoke induces CYP1A2 and lowers clozapine levels, the same effect tobacco has. Stopping smoking can raise levels sharply.
What to do: Levels change on starting OR stopping. Monitor around either. Edibles do not do this.
Source: Pharmacokinetic interactions between cannabis products and conventional medications · PMID 31433338Olanzapine
ZyprexaSmoke induced CYP1A2 lowers olanzapine levels.
What to do: Reassess if symptom control changes with smoking habits. Edibles do not do this.
Source: Pharmacokinetic interactions between cannabis products and conventional medications · PMID 31433338Warfarin
CoumadinRaised INR and bleeding risk have been reported repeatedly with added CBD.
What to do: Check INR more often when starting, changing, or stopping CBD.
Source: Pharmacokinetic interactions between cannabis products and conventional medications · PMID 31433338Ketoconazole
Slows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Itraconazole
SporanoxSlows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Clarithromycin
BiaxinSlows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Erythromycin
Slows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Ritonavir
NorvirSlows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Grapefruit juice
Slows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Fluconazole
DiflucanSlows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Amiodarone
CordaroneSlows the enzyme that clears THC, so THC levels rise and effects can be stronger or last longer than expected.
What to do: Expect more intoxication from the same dose. Start lower.
Source: FDA dronabinol (Syndros) label, section 7.2Cyclosporine
NeoralTHC is highly protein bound and can displace other protein-bound drugs, raising their free active fraction.
What to do: Monitor for added effects when starting THC or raising the dose.
Source: FDA dronabinol (Syndros) label, section 7.3Amphotericin B
THC is highly protein bound and can displace other protein-bound drugs, raising their free active fraction.
What to do: Monitor for added effects when starting THC or raising the dose.
Source: FDA dronabinol (Syndros) label, section 7.3Warfarin
CoumadinTHC can displace warfarin from plasma proteins and raise its free fraction, adding to bleeding risk.
What to do: Check INR more often when starting or changing THC.
Source: FDA dronabinol (Syndros) label, section 7.3Alcohol
Sedative effects were additive when tested together in humans.
What to do: Expect more drowsiness and worse coordination than either alone. Do not drive.
Source: FDA nabilone (Cesamet) label, drug interactionsDiazepam
ValiumSedative effects were additive when tested together in humans.
What to do: Expect more drowsiness and worse coordination than either alone. Do not drive.
Source: FDA nabilone (Cesamet) label, drug interactionsSecobarbital
Sedative effects were additive when tested together in humans.
What to do: Expect more drowsiness and worse coordination than either alone. Do not drive.
Source: FDA nabilone (Cesamet) label, drug interactionsCodeine
Sedative effects were additive when tested together in humans.
What to do: Expect more drowsiness and worse coordination than either alone. Do not drive.
Source: FDA nabilone (Cesamet) label, drug interactionsAmphetamines
AdderallAdditive high blood pressure and fast heart rate, with possible strain on the heart.
What to do: Relevant with any existing heart condition. Discuss before combining.
Source: FDA nabilone (Cesamet) label, drug interactionsCocaine
Additive high blood pressure and fast heart rate, with possible strain on the heart.
What to do: Relevant with any existing heart condition. Discuss before combining.
Source: FDA nabilone (Cesamet) label, drug interactionsPseudoephedrine
SudafedAdditive high blood pressure and fast heart rate, with possible strain on the heart.
What to do: Relevant with any existing heart condition. Discuss before combining.
Source: FDA nabilone (Cesamet) label, drug interactionsAtropine
Additive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsScopolamine
Additive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsDiphenhydramine
BenadrylAdditive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsAmitriptyline
ElavilAdditive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsAmoxapine
Additive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsDesipramine
NorpraminAdditive or greater than additive fast heart rate and drowsiness.
What to do: Watch for palpitations and heavy sedation, particularly in older adults.
Source: FDA nabilone (Cesamet) label, drug interactionsOmeprazole
PrilosecWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Omeprazole is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Omeprazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Esomeprazole
NexiumWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Esomeprazole is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Esomeprazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Lansoprazole
PrevacidWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Lansoprazole is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Lansoprazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Pantoprazole
ProtonixWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Pantoprazole is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Pantoprazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Escitalopram
LexaproWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Escitalopram is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Escitalopram levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Citalopram
CelexaWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Citalopram is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Citalopram levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Sertraline
ZoloftWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Sertraline is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Sertraline levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Diazepam
ValiumWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Diazepam is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Diazepam levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Phenytoin
DilantinWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Phenytoin is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Phenytoin levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Voriconazole
VfendWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Voriconazole is cleared from the body by CYP2C19.
- Slowing that clearance down would raise Voriconazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Clopidogrel
PlavixWhy this is flagged
- CBD is a moderate inhibitor of CYP2C19. FDA Epidiolex label, section 7.2
- Clopidogrel has to be activated by CYP2C19 before it can work.
- Blocking that step would leave less active drug, so Clopidogrel could work less well rather than more strongly.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Metoprolol
LopressorWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Metoprolol is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Metoprolol levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Carvedilol
CoregWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Carvedilol is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Carvedilol levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Propranolol
InderalWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Propranolol is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Propranolol levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Risperidone
RisperdalWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Risperidone is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Risperidone levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Haloperidol
HaldolWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Haloperidol is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Haloperidol levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Aripiprazole
AbilifyWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Aripiprazole is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Aripiprazole levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Paroxetine
PaxilWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Paroxetine is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Paroxetine levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Venlafaxine
EffexorWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Venlafaxine is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Venlafaxine levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Amitriptyline
ElavilWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Amitriptyline is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Amitriptyline levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Nortriptyline
PamelorWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Nortriptyline is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Nortriptyline levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Desipramine
NorpraminWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Desipramine is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Desipramine levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Atomoxetine
StratteraWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Atomoxetine is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Atomoxetine levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Dextromethorphan
Why this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Dextromethorphan is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Dextromethorphan levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Ondansetron
ZofranWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Ondansetron is cleared from the body by CYP2D6.
- Slowing that clearance down would raise Ondansetron levels, so effects and side effects may be stronger.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Codeine
Why this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Codeine has to be activated by CYP2D6 before it can work.
- Blocking that step would leave less active drug, so Codeine could work less well rather than more strongly.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Tramadol
UltramWhy this is flagged
- CBD inhibits CYP2D6. Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735)
- Tramadol has to be activated by CYP2D6 before it can work.
- Blocking that step would leave less active drug, so Tramadol could work less well rather than more strongly.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Duloxetine
CymbaltaWhy this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Duloxetine is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Duloxetine levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Fluvoxamine
LuvoxWhy this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Fluvoxamine is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Fluvoxamine levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Imipramine
TofranilWhy this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Imipramine is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Imipramine levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Tizanidine
ZanaflexWhy this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Tizanidine is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Tizanidine levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Melatonin
Why this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Melatonin is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Melatonin levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
Naproxen
AleveWhy this is flagged
- Smoked cannabis induces CYP1A2 through the combustion products in the smoke, not through THC itself. Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338)
- Naproxen is cleared from the body by CYP1A2.
- Speeding that clearance up would lower Naproxen levels, so the usual dose may do less.
This specific pairing has not been studied. It is reasoning from the enzyme, not a measured result.
No match for that medication. That does not mean it is safe to combine, only that we have nothing documented or predicted for it. Ask your pharmacist.
How cannabis changes drug metabolism
Almost every interaction below comes down to the liver enzymes that clear medications from the body. These are the specific effects, and the source for each.
| Exposure | Enzyme | Effect | Evidence |
|---|---|---|---|
| CBD | CYP2C19 | moderate inhibitor | FDA Epidiolex label, section 7.2 |
| CBD | CYP2D6 | inhibitor | Jiang et al., CBD as a potent atypical CYP2D6 inhibitor (PMID 21821735) |
| CBD | UGT1A9 | inhibitor | FDA Epidiolex label, section 7.2 |
| CBD | CYP2B6 | inducer and inhibitor | FDA Epidiolex label, section 7.2 |
| CBD | CYP1A2 | weak inhibitor | FDA Epidiolex label, section 7.2 |
| CBD | CYP3A4 / CYP2C19 | substrate | FDA Epidiolex label, section 7.1: rifampin lowered CBD exposure by 32% |
| THC | CYP2C9 and CYP3A4 | substrate | Exogenous cannabinoids as substrates, inhibitors and inducers (PMID 24160757) |
| THC | CYP1A2, CYP2B6, CYP2C9, CYP2D6 | competitive inhibitor in vitro | Cannabinoid metabolites as CYP450 inhibitors (PMID 34493602) |
| Smoked cannabis | CYP1A2 | inducer, via combustion products | Pharmacokinetic interactions between cannabis products and conventional medications (PMID 31433338) |
Two Footnotes
Smoking is not the same as an edible. The drop in clozapine, olanzapine and theophylline levels comes from the polycyclic aromatic hydrocarbons in smoke, exactly as with tobacco, not from THC. An edible or tincture at the same dose does not do it. Every smoke-driven row here is tagged as such.
For some drugs, less is the danger. Codeine, tramadol and tamoxifen only work after the body converts them, and CYP2D6 does the converting. Blocking that enzyme means less active drug, not more. Those rows say “may work less well” rather than showing a rising arrow, because treating them as an overdose risk gets the clinical response backwards.
Where this comes from
Label rows are taken from current FDA prescribing information. Study rows cite papers held in the CannaBase research database, which you can open and read in full. Predicted rows are derived from documented enzyme effects and are labelled throughout as predictions rather than findings. Reviewed for clinical accuracy before publication. Last updated August 2026.