Drug & supplement interaction

Ostarine + Zafirlukast

Zafirlukast brand name: Accolate.

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

Zafirlukast falls into 2 drug categories that Ostarine can interact with; the most serious is rated minor. 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.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Ostarine and Zafirlukast

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Ostarine interacts with whole categories of medication. Zafirlukast falls into 2 of those categories, so it can interact with Ostarine in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Minor).

Minor

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS

1 of 2

Why this applies to Zafirlukast

Zafirlukast falls under CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS — the group Ostarine interacts with.

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.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for this pairing: Zafirlukast (Accolate) is a mild blocker of a liver enzyme called CYP3A4. Ostarine is partly broken down by that same enzyme. So in theory, taking them together could slow Ostarine's breakdown a little and let more of it build up, which might mean stronger effects and more of Ostarine's potential harms, like liver stress.

In real life, this is pretty unlikely to matter. When researchers paired Ostarine with itraconazole, a much stronger 3A4 blocker than zafirlukast, Ostarine levels barely budged. My bigger concern is Ostarine itself. It's an unapproved SARM that's been linked to liver injury and isn't recommended for general use. Please talk with your pharmacist or doctor before combining anything with it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Coss CC, Jones A, Dalton JT. Pharmacokinetic drug interactions of the selective androgen receptor modulator GTx-024 (enobosarm) with itraconazole, rifampin, probenecid, celecoxib and rosuvastatin. Invest New Drugs 2016;34(4):458-67. PubMed
Minor

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 2

Zafirlukast also falls under 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.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the short version: your asthma medicine zafirlukast (Accolate) is cleared by a liver enzyme called CYP2C9. In a test tube, Ostarine looked like it could slow that enzyme down, which in theory might let zafirlukast build up a bit and lead to stronger effects like headache, nausea, or stomach upset. But here's the reassuring part. When this was actually studied in people, Ostarine did not meaningfully change how this enzyme works, so a real-world problem here is unlikely.

That said, Ostarine is an unapproved SARM that's been tied to liver injury, and zafirlukast can also stress the liver. I'd run any plans to use it past your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Coss CC, Jones A, Dalton JT. Pharmacokinetic drug interactions of the selective androgen receptor modulator GTx-024 (enobosarm) with itraconazole, rifampin, probenecid, celecoxib and rosuvastatin. Invest New Drugs 2016;34(4):458-67. 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

Ostarine Also Interacts With Other Medications

Ostarine has 440 moderate, 170 minor known drug interactions in our database — the Zafirlukast one above is among them. If you take anything else, check it against the full list below.

Moderate 440 Minor 170 No known interaction 2,220 (incl. Zafirlukast)
Taking anything else?

Check Another of Your Medications Against Ostarine

Covers the 2,830 medications we’ve checked against Ostarine. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Zafirlukast

This page covers Ostarine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zafirlukast page lists 88 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Adrafinil (moderate), African Wild Potato (moderate), Bacopa (moderate) and Berberine (moderate).

By severity: 1 major · 64 moderate · 23 minor.

Open the Zafirlukast interaction page

One more smart check

Taking Ostarine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 33 real supplement products containing Ostarine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ostarine. Your product may carry other ingredients that interact with Zafirlukast too, on top of Ostarine — 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 Ostarine and Zafirlukast 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 Ostarine
Steady interest

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

29 days ago today
Medication Zafirlukast
Top half

#1,383 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 Ostarine

What is Ostarine?

  • Muscle building
  • Athletic performance
  • Fat loss / body recomposition
  • Bodybuilding cycles

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.

Read the full Ostarine monograph & all interactions
Medication

About Zafirlukast

What Is Zafirlukast Used For?

Brand name: Accolate

Zafirlukast tablets are used for the prophylaxis (prevention) and chronic treatment of asthma in adults and children 5 years of age and older. It is taken daily to help control ongoing asthma symptoms — not to relieve a sudden asthma attack.

It is available under the brand names Accolate and Zafirlukast as an oral tablet.

See full Zafirlukast drug information
Keep checking

Other Drugs & Ostarine

Browse every other medication we’ve checked against Ostarine — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
440Moderate
170Minor
2,219No known interaction
440 Moderate 170 Minor 2,219 No interaction
Moderate

440 interactions

Showing 60 of 440 moderate interactions — see all 440 on the Ostarine page.

Minor

170 interactions

Showing 60 of 170 minor interactions — see all 170 on the Ostarine page.

No interaction 2,219 drugs checked — show the list

We also checked Ostarine against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,219 medications checked with no known interaction — see the full Ostarine list.

See the full Ostarine interactions page
See every supplement checked against Zafirlukast, 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
Ostarine monograph › Uses, safety, and every drug interaction in one place Zafirlukast supplement interactions › Every supplement checked against Zafirlukast, ranked by severity Zafirlukast 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 Ostarine and Zafirlukast Together: Common Questions

Can you take Ostarine with Zafirlukast?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Ostarine and Zafirlukast?
Zafirlukast belongs to more than one drug category, and Ostarine 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 Ostarine and Zafirlukast interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Zafirlukast and Ostarine?

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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.