Weed and Antibiotics: Which Ones Actually Interact

Most antibiotics have no known interaction with cannabis and no mechanism that would produce one. A short list does, and the reason is narrow enough to state precisely: THC and CBD are cleared by the liver enzyme CYP3A4, so an antibiotic that strongly induces or inhibits CYP3A4 will move cannabis levels. Almost no antibiotics do that. The ones that do are worth knowing by name.

Can You Take Antibiotics While Using Cannabis?

For the antibiotics most people are actually prescribed, there is no documented interaction and no established mechanism for one.

The exception is a small group that acts on CYP3A4. One of them, rifampin, has been measured directly with cannabinoids in humans, and the effect was large. Two others, erythromycin and clarithromycin, act on the same enzyme in the opposite direction and have not been measured with cannabis but have a well characterized mechanism.

That is the whole picture. What follows separates the ones with evidence from the ones without, and says plainly which is which.

Which Antibiotics Actually Matter?

Three, on current evidence:

• Rifampin, which strongly induces CYP3A4 and substantially lowers cannabis exposure. Directly measured.
• Erythromycin, a mechanism-based CYP3A4 inhibitor, which would be expected to raise it.
• Clarithromycin, also a mechanism-based CYP3A4 inhibitor, same expected direction.

Everything else in common outpatient use, including amoxicillin, doxycycline, ciprofloxacin, azithromycin and metronidazole, has no published cannabis interaction study and no strong CYP3A4 activity that would predict one.

Rifampin and Cannabis

This is the one case where the question has an actual answer, because rifampin was one of the drugs tested.

In a Phase 1 open-label randomized crossover study, 36 healthy male volunteers in three parallel groups of 12 received a THC and CBD oromucosal spray delivering 10.8 mg THC and 10 mg CBD. One group also received rifampin at 600 mg daily for 10 days.

Every measured analyte dropped:

The collapse in 11-hydroxy-THC is the striking result. That compound is the active metabolite responsible for much of the effect felt after oral cannabis, and rifampin removed roughly nine tenths of it. The authors concluded that all three analytes are CYP3A4 substrates, and that CYP3A4 handles not only THC and CBD but the onward metabolism of 11-hydroxy-THC as well.

Practically: a patient on rifampin should expect the same cannabis product to do noticeably less. The risk that creates is not toxicity. It is redosing to chase an effect that the antibiotic is actively removing.

Rifampin is used for tuberculosis and for certain serious staphylococcal infections. It is not a drug anyone takes casually, and its course is usually long, which makes this worth raising with the prescriber rather than working around.

Clarithromycin and Erythromycin

These two run the enzyme in the opposite direction. Both are documented mechanism-based inhibitors of CYP3A4, meaning they inactivate the enzyme in a time-dependent way rather than simply competing with it for a moment.

No study has measured either one with cannabis. What the same rifampin trial provides is the other half of the picture, because a second group received ketoconazole at 400 mg daily for 5 days, a strong CYP3A4 inhibitor used here as the inhibitor arm:

Blocking CYP3A4 nearly quadrupled exposure to the active metabolite. Ketoconazole is not an antibiotic and it is not clarithromycin, so those numbers are not a prediction for the macrolides. They establish the direction and the rough scale of what strong CYP3A4 inhibition does to cannabinoids, which is the useful part.

If you are prescribed erythromycin or clarithromycin and you use cannabis, the reasonable expectation is a stronger and longer effect from the same amount, not a weaker one.

Azithromycin and Cannabis

Azithromycin, the drug in a Z-Pak, is the macrolide that behaves differently, and this is a genuine distinction rather than a hedge.

Erythromycin and clarithromycin both show time-dependent inhibition of CYP3A4. Azithromycin does not share that inhibitory behavior. Among the three macrolides it is the one with the least mechanistic reason to affect cannabis levels.

That does not make it studied. It makes it the macrolide least likely to matter.

Amoxicillin, Doxycycline, Ciprofloxacin and Metronidazole

These are the antibiotics most people are actually handed, and they are grouped here deliberately, because the honest answer for all four is the same and it is not a clean bill of health.

No published study has measured any of them with cannabis. None is a strong CYP3A4 inducer or inhibitor, so there is no established mechanism that would predict a meaningful change in cannabis levels. That is a reason the question is low priority, not a reason it has been answered.

This article deliberately stops there rather than reasoning further per drug. Working out each one's full metabolic profile and whatever secondary pathways might apply is a research task that has not been done here, and filling the gap with confident-sounding pharmacology would be exactly the wrong move on a question a patient might act on.

One specific point of confusion is worth clearing up. Metronidazole, sold as Flagyl, carries a well known warning about alcohol. That warning is about alcohol. It is not a cannabis warning, and it should not be read across to cannabis.

Does Cannabis Make Antibiotics Less Effective?

No evidence supports this, and the measured effects run the other way.

Everything above describes antibiotics changing cannabis levels. The reverse question, whether cannabinoids alter antibiotic concentrations or reduce how well an antibiotic clears an infection, does not have supporting evidence behind it.

Finish the course you were prescribed. Stopping an antibiotic early has real consequences that are far better documented than anything on this page.

What Should You Tell Your Physician?

Name the antibiotic. That is the entire ask, because the answer depends almost completely on which one it is.

If it is rifampin, erythromycin or clarithromycin, say that you use cannabis and roughly how much. If it is one of the common ones, it is still worth mentioning, and it is unlikely to change anything. Also mention it if you use a high cannabidiol product, since cannabidiol acts on several liver enzymes in its own right.

What This Means for Florida, Georgia, and Texas Patients

An antibiotic course is temporary and is not a barrier to certification in any of the three state programs. Miracle Leaf® physicians review a medication list as part of the evaluation, and a short course of amoxicillin is not the part of that list anyone is concerned about.

The programs and their condition lists differ by state, and the Florida marijuana laws, Georgia marijuana laws, and Texas marijuana laws pages cover each one. The Florida, Georgia, and Texas program pages cover how certification works.

What If You Live Outside Florida, Georgia, and Texas?

Miracle Leaf® operates clinics in Florida, Georgia, and Texas and offers telehealth evaluations in a number of additional states. The telehealth page covers which states are served. If yours is not among them, the states where cannabis is legal post covers the national picture.

Sources for Cannabis and Antibiotic Interactions

• A Phase I, open-label, randomized, crossover study in three parallel groups to evaluate the effect of Rifampicin, Ketoconazole, and Omeprazole on the pharmacokinetics of THC/CBD oromucosal spray in healthy volunteers. Stott C, White L, Wright S, et al. SpringerPlus. 2013;2:236. doi:10.1186/2193-1801-2-236. PMCID PMC3671111. Source of the study design and subject count, the rifampin and ketoconazole dosing, every percentage change reported in both tables above, and the conclusion that THC, CBD and 11-hydroxy-THC are CYP3A4 substrates.
• Time-dependent inhibition of CYP3A4-mediated midazolam metabolism by macrolide antibiotics in CYP3A4 genetic variants. Source of the mechanism-based CYP3A4 inhibition shown by erythromycin and clarithromycin, and of azithromycin not sharing that behavior.
• Mechanism-based inhibition profiles of erythromycin and clarithromycin with cytochrome P450 3A4 genetic variants. Source of the time-dependent inhibition characterization for both macrolides.
• Macrolides. StatPearls, NCBI Bookshelf. Background on the macrolide class and its members.

Related Health and Eligibility Resources

• The cannabis and ibuprofen post covers NSAIDs, where the enzyme in question is CYP2C9 rather than CYP3A4 and the cannabidiol content is what matters.
• The cannabis and Xanax post covers benzodiazepines, where CYP3A4 appears again from the other side.
• The cannabis and antidepressants post covers SSRIs and SNRIs.
• The qualifying conditions page covers eligibility across all three state programs.

Talk to a Physician About Your Medication List

Bring the name of the antibiotic. With this question the name is most of the answer.

Call (833) LEGAL-MJ or contact us online to book. Evaluation pricing is on the pricing page, and the clinicians who review this content are listed on the editorial team page.

Disclaimer

This post is informational and is not medical advice. No study has measured cannabis with any antibiotic other than rifampin. The rifampin and ketoconazole figures come from a 36 subject study of a pharmaceutical THC and CBD oromucosal spray in healthy male volunteers, and do not necessarily describe smoked, vaporized or edible cannabis in a patient population. Ketoconazole is an antifungal, not an antibiotic, and is cited here only to establish the direction and scale of strong CYP3A4 inhibition. The expectations stated for erythromycin and clarithromycin are mechanistic inferences, not measurements. Amoxicillin, doxycycline, ciprofloxacin and metronidazole are described here as unstudied rather than as safe, and this article does not attempt to resolve them. Do not stop or alter a prescribed antibiotic based on this article. Discuss cannabis use with the physician who prescribed it.