Herb & supplement monograph

Ostarine Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Ostarine interacts with medications. The heart of this page is the interaction list — every drug Ostarine is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Ostarine is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Ostarine Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, no major Ostarine drug interactions have been identified, and the overall risk of a clinically significant interaction appears modest for most people. None of the interactions are rated major, and even the moderate ones rest mostly on theoretical or limited evidence rather than proven harm in people.

Interactions deserving the most attention

The concern with the strongest footing involves the liver. Ostarine has raised liver enzyme markers in some people, and the FDA has linked SARM products to reports of liver toxicity, so combining it with hepatotoxic drugs deserves the most caution. Human studies also show that rifampin can cut ostarine levels substantially, which may blunt its effects, while probenecid does the opposite, raising ostarine levels by slowing how the body clears it.

What the rest of the list means

A long interaction list does not mean every combination is risky. Most entries are predictions based on how the body's enzymes process ostarine, and some predicted effects have already been ruled out; for example, human research found that ostarine does not meaningfully affect one enzyme it was expected to block, and a strong enzyme blocker barely changed ostarine levels.

Check your medications against Ostarine

Based on HelloPharmacist’s Ostarine interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Ostarine

613 medications have a known interaction with Ostarine, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Ostarine using our pharmacist-reviewed interaction data.

AI summaries are generated from our Ostarine interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Ostarine combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Ostarine affects

Every type of medication (drug category) Ostarine is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 6 drug categories Ostarine interacts with

Cytochrome P450 3a4 (cyp3a4) InducersHepatotoxic DrugsProbenecid (benemid)Rifampin (rifadin)Cytochrome P450 2c9 (cyp2c9) SubstratesCytochrome P450 3a4 (cyp3a4) Inhibitors

Cytochrome P450 3A4 (Cyp3A4) Inducers

Theoretically, concomitant use of ostarine with CYP3A4 inducers could decrease the clinical effects of ostarine.
Ostarine is partially metabolized by CYP3A4. Clinical research shows that taking rifampin, a potent inducer of CYP3A4, reduces the maximum plasma concentration of ostarine by 23% and the area under the curve by 43%.

Likelihood Possible Evidence B

Hepatotoxic Drugs

Theoretically, concomitant use with hepatotoxic drugs might increase the risk of adverse hepatotoxic effects.
Some clinical research shows that ostarine can increase alanine aminotransferase, a marker of liver damage, in some patients. Additionally, the U.S. Food and Drug Administration warns that supplements containing SARMs, such as ostarine, have been associated with reports of liver toxicity and there are at least two reports of drug-induced liver injury attributed to the use of ostarine.

Likelihood Possible Evidence D

Probenecid (Benemid)

Theoretically, concomitant use of ostarine with probenecid could increase the effects and adverse effects of ostarine.
Clinical research shows that probenecid increases ostarine levels and slows the clearance of ostarine, likely via inhibition of UDP-glucuronosyltransferase (UGT). Ostarine is partially metabolized by UGT.

Likelihood Possible Evidence B

Rifampin (Rifadin)

Theoretically, concomitant use of ostarine with rifampin could decrease the clinical effects of ostarine.
Clinical research shows that taking rifampin with ostarine reduces the maximum plasma concentration of ostarine by 23% and the area under the curve by 43%. Ostarine is partially metabolized by cytochrome P450 3A4 (CYP3A4), and rifampin is a potent CYP3A4 inducer.

Likelihood Possible Evidence B

Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, ostarine might increase levels of drugs metabolized by CYP2C9, although clinical research suggests this is not clinically relevant.
Although in vitro research suggests that ostarine inhibits CYP2C9, more robust clinical research shows that ostarine does not significantly affect CYP2C9.

Likelihood Unlikely Evidence B

Cytochrome P450 3A4 (Cyp3A4) Inhibitors

Theoretically, concomitant use of ostarine with CYP3A4 inhibitors could increase the effects and adverse effects of ostarine, although this is unlikely to be clinically significant.
Ostarine is partially metabolized by CYP3A4. However, clinical research shows that taking itraconazole, a potent inhibitor of CYP3A4, had minimal effects on the levels of ostarine in the body.

Likelihood Unlikely Evidence B

Monograph

Ostarine: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Ostarine (also called MK-2866 or enobosarm) is an experimental, unapproved drug known as a SARM (selective androgen receptor modulator), not a true dietary supplement. It is not approved by the FDA, is banned in sports, and has been linked to liver injury and other serious harms, so it is not recommended for general use.

Part used: Synthetic compound (not from a plant)
Common forms: Capsules, tablets, liquids, powders sold as research chemicals or 'sports supplements'

People commonly use it for

Muscle building
Athletic performance
Fat loss / body recomposition
Bodybuilding cycles

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallBest avoided

Ostarine is an unapproved investigational drug with documented safety risks and no FDA approval.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Ostarine, also known as MK-2866 or enobosarm, is a man-made chemical in a class called selective androgen receptor modulators (SARMs). It is not an herb or a plant product. It was originally developed by drug companies as a possible treatment for muscle wasting and other conditions.

Even though it is sometimes sold online or in stores as a "dietary supplement" or "research chemical," Ostarine is not an approved drug and is not a legal dietary supplement in the United States. The FDA has warned companies for marketing SARMs in products meant for bodybuilding and athletic performance.

People most often use Ostarine in an attempt to build muscle, lose fat, and improve workout results. These uses are not approved or proven safe.

How it works

Ostarine is designed to attach to androgen receptors, the same receptors that respond to testosterone. The idea behind SARMs is that they may act on muscle and bone tissue while having less effect on other organs, compared with traditional anabolic steroids.

By turning on these receptors, Ostarine may signal the body to build muscle and increase strength. Much of this understanding comes from laboratory and early clinical research, and the way it behaves in the human body over time is still not fully understood.

Even though it is marketed as "selective," it can still affect hormone levels and other body systems in ways that may cause harm.

Effectiveness

Does Ostarine work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 6 uses evaluated

6 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Ostarine, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 6 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Athletic performance