Yes, CBD interacts with other medicines. It slows several of the liver enzymes that clear medicines from the body, so blood levels of some medicines rise, and a few medicines change CBD levels in return.1 The best-proven interactions are with the anti-seizure medicines clobazam and valproate. The ones a systematic review rated as potentially highest risk are warfarin, valproate, tacrolimus and sirolimus.2
How does CBD interact with medicines?
There are three main ways.
- CBD blocks enzymes that break down other medicines. The body clears many medicines using a family of liver enzymes called cytochrome P450 (CYP), and another family called UGT. CBD is a moderate blocker of CYP2C19 and a weak blocker of CYP1A2. It also affects CYP2B6, CYP2C8, CYP2C9, UGT1A9 and UGT2B7, and a transport protein called P-glycoprotein (P-gp).13 When an enzyme is blocked, medicines that depend on it can build up.
- Other medicines change CBD levels. CBD itself is broken down by CYP2C19 and CYP3A4. Medicines that speed up those enzymes lower CBD levels.1
- Effects add together. CBD can cause sleepiness, so it adds to alcohol and sedating medicines. It can raise liver enzymes, which matters alongside other medicines that stress the liver.1
CBD interactions by medicine
“How sure are we” reflects the type of evidence. A dedicated study in people is strongest. A prediction from laboratory work is weakest. The last column describes what the prescribing information and published reports say prescribers typically do. It is not advice to change your own medicines.
| Medicine or class | What happens | How sure are we | What a prescriber typically does |
|---|---|---|---|
| Clobazam (anti-seizure) | The active breakdown product of clobazam rises about 3-fold (3 to 4-fold in the Australian product information). Sleepiness affected 46% of people on both, against 16% on CBD without clobazam. The interaction runs both ways.13 | High. Dedicated studies and controlled trials. | Watches for sedation and considers a lower clobazam dose. |
| Valproate (anti-seizure, mood) | More liver enzyme rises. Enzymes above 3 times the normal limit occurred in 21% of people on CBD plus valproate, 30% with clobazam as well, and 3% on neither. Valproate blood levels barely change. The mechanism is unknown.13 | High. Controlled trials. | Orders liver blood tests more often and adjusts one or both medicines if enzymes rise. |
| Stiripentol (anti-seizure) | Stiripentol exposure rose 55% in healthy volunteers.1 | High. Dedicated study. | Monitors for stiripentol side effects. |
| Phenytoin, lamotrigine (anti-seizure) | Levels may rise. Predicted from laboratory data; no formal studies in people.3 | Low to moderate. | Starts the combination cautiously and reviews doses if side effects appear. |
| Everolimus, sirolimus, tacrolimus (transplant and cancer medicines) | Everolimus exposure rose about 2.5-fold. One case report describes about a 3-fold rise in tacrolimus in a person taking 2,000 to 2,900 mg of CBD a day. In a series of 25 patients on everolimus or sirolimus, levels rose in 76%.12 | High for everolimus. Case reports and a case series for the others. | Measures blood levels of the transplant medicine and adjusts its dose. |
| Warfarin (blood thinner) | Case reports of INR rising after prescription CBD was started. In one, INR ranged up to 6.86 as CBD was increased, and the warfarin dose was cut by about 30%.2 The Australian product information also predicts an interaction through CYP2C9.3 | Moderate. Case reports plus a plausible mechanism. | Checks INR more often when CBD is started, stopped or changed. |
| Digoxin (heart) | Levels may rise through the P-gp transporter.1 | Low. Predicted. | Considers monitoring digoxin levels. |
| Clopidogrel (anti-platelet) | Clopidogrel must be activated by CYP2C19. CBD may reduce the active form, which could make it less effective.1 | Low. Predicted. | Reviews whether the combination is suitable. |
| Citalopram, escitalopram (antidepressants) | Citalopram blood levels rose in six young people after CBD 200 to 800 mg a day was added. Whether this caused more side effects was not established.4 | Low. One small study. | Watches for new antidepressant side effects. |
| Methadone | One case report: a 13-year-old’s methadone level fell from 271 to 125 ng/mL after CBD was stopped, and her sleepiness improved.5 | Low. Single case. | Asks about CBD use and watches for sedation. |
| Omeprazole and other CYP2C19 medicines | Levels may rise.3 | Low. Predicted from laboratory data. | Considers a lower dose for sensitive medicines. |
| Morphine, lorazepam (cleared by UGT2B7) | Levels may rise.3 | Low. Predicted from laboratory data. | Reviews doses if side effects appear. |
| Theophylline, tizanidine, caffeine | Caffeine exposure rose 95% in a study. Theophylline and tizanidine use the same enzyme (CYP1A2).1 | High for caffeine. Predicted for the others. | Considers lower doses of medicines where small changes matter. |
| Alcohol, benzodiazepines, opioids, sleeping tablets | Added sleepiness. Alcohol also raised peak CBD blood levels by 93%.1 | Moderate. | Advises caution with sedating combinations. |
| Rifampicin and other strong enzyme inducers | CBD levels fell by about 32%.1 | High. Dedicated study. | Reviews the CBD dose. |
Not every medicine is affected. In studies, CBD did not change levels of midazolam, a sensitive marker for the CYP3A4 enzyme. The antifungals itraconazole and fluconazole, which block the enzymes that clear CBD, changed CBD levels by amounts the label calls not clinically meaningful.1
Do interactions happen at low doses?
This is the main gap. The measured interactions in the table mostly used 750 mg twice a day in healthy volunteers, or 10 to 25 mg per kg a day in people with epilepsy.1 Enzyme blocking generally depends on dose, so smaller doses should have smaller effects. But “should” is not evidence, and nobody has mapped a dose below which interactions stop.
Regulators have taken a cautious line. The United Kingdom’s Food Standards Agency advises people on prescription medicines not to take CBD food supplements without advice from a medical professional, even at its recommended limit of 10 mg a day.6
For medicines with a narrow margin between a helpful dose and a harmful one (warfarin, transplant medicines, some anti-seizure medicines, digoxin), a small change in blood level can matter.1
What about common medicines not in the table?
People often ask about blood pressure tablets, statins, paracetamol, anti-inflammatories, melatonin, the contraceptive pill and hormone therapy. Our research did not find verified studies of CBD with these medicines, so we cannot say what happens. An absence of studies is not proof of safety. A pharmacist can check your specific medicines against current interaction databases.
One finding worth knowing: in a trial of 600 mg of CBD a day added to 3 g of paracetamol a day for knee osteoarthritis, liver enzyme rises were more common with CBD (15 participants) than placebo (5 participants).7 The trial was not designed to show whether paracetamol played a part.
The prescribing information says there are not enough data to assess the risk of combining CBD with other medicines that can affect the liver.1
Does food change the picture?
Yes, indirectly. Taking CBD with a high-fat meal raises CBD blood levels about 4 to 5-fold compared with an empty stomach.1 Higher CBD levels mean more enzyme blocking. This is why prescribers ask people to take CBD the same way each day. See Taking CBD with food.
CBD also lingers. After a week of twice-daily dosing its half-life (the time for blood levels to halve) is 56 to 61 hours, so interactions do not switch off the day CBD is stopped.1
What to do if you take other medicines
- Give your prescriber and pharmacist a full list, including over-the-counter products, supplements and any CBD or cannabis product, whatever its source.
- Ask whether any of your medicines need a blood test or dose review. Prescribers decide whether to adjust anything.
- Talk to your prescriber before you make any change to a prescribed medicine or to CBD. Sudden changes can be risky, particularly with anti-seizure medicines.1
- Report new sleepiness, bruising or bleeding, or signs of a liver problem. See CBD side effects and CBD and the liver.
In Australia, CBD is a prescription medicine, so a prescriber and a pharmacist are expected to check for interactions before it is dispensed. Products obtained outside that system are not checked. See Who should not take CBD?.
Footnotes
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Jazz Pharmaceuticals. Epidiolex (cannabidiol) oral solution, US prescribing information, DailyMed (accessed November 2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8bf27097-4870-43fb-94f0-f3d0871d1eec ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16 ↩17 ↩18 ↩19 ↩20
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Nachnani R and others. Systematic review of drug-drug interactions of delta-9-tetrahydrocannabinol, cannabidiol, and Cannabis. Frontiers in Pharmacology, 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11167383/ ↩ ↩2 ↩3
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Therapeutic Goods Administration. Epidyolex (cannabidiol) Australian Product Information, version attached to the AusPAR, January 2021 (may be superseded). https://www.tga.gov.au/sites/default/files/auspar-cannabidiol-210115-pi.pdf ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7
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Anderson LL and others. Citalopram and cannabidiol: in vitro and in vivo evidence of pharmacokinetic interactions relevant to the treatment of anxiety disorders in young people. Journal of Clinical Psychopharmacology, 2021. https://doi.org/10.1097/JCP.0000000000001427 ↩
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Madden K, Tanco K, Bruera E. Clinically significant drug-drug interaction between methadone and cannabidiol. Pediatrics, 2020. https://doi.org/10.1542/peds.2019-3256 ↩
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UK Food Standards Agency and Food Standards Scotland. Provisional cannabidiol (CBD) acceptable daily intake: lay summary, October 2023. https://www.gov.uk/government/publications/provisional-cannabidiol-cbd-acceptable-daily-intake-adi/lay-summary ↩
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Pramhas S and others. Randomised trial of cannabidiol 600 mg a day added to paracetamol for knee osteoarthritis. The Lancet Regional Health Europe, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10682664/ ↩
Common questions
Can I take CBD with my other medications?
That is a question for your prescriber or pharmacist, because the answer depends on the medicine, the CBD dose and your health. CBD can raise blood levels of medicines broken down by certain liver enzymes. The interactions of most concern involve clobazam, valproate, warfarin and transplant medicines.
Does CBD interact with antidepressants?
The evidence is limited. In a small Australian study, six young people taking citalopram or escitalopram had higher citalopram blood levels after CBD was added. Laboratory tests in the same study found only minimal effects on sertraline, fluoxetine and mirtazapine. Tell your prescriber if you take an antidepressant.
Does CBD interact with blood thinners like warfarin?
There are published case reports of INR, the blood test used to monitor warfarin, rising after CBD was started, with warfarin doses needing to be cut by about 20 to 30 per cent. A systematic review ranks warfarin among the highest-risk CBD interactions. Our research did not find verified data on newer blood thinners such as apixaban.
Can I take CBD with benzodiazepines or sleeping tablets?
CBD can cause sleepiness, and the prescribing information warns that other sedating medicines and alcohol can add to it. With the benzodiazepine clobazam there is also a proven blood-level interaction, and 46% of trial participants taking both had sleepiness or sedation. Ask your prescriber or pharmacist before combining them.
This page is general information, not medical or legal advice. Laws and evidence change; we show the date we last checked the facts at the top of every page. Talk to your doctor or pharmacist before starting, stopping or changing any medicine.
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