Drug & supplement interaction

Ipriflavone + Zileuton

Zileuton brand names: Zyflo, Zyflo CR.

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

Zileuton falls into 2 drug categories that Ipriflavone can interact with; the most serious is rated moderate. Ipriflavone is thought to competitively inhibit cytochrome P450 1A2 (CYP1A2).

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Ipriflavone and Zileuton

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

Why Are There 2 Interactions?

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

Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

1 of 2

Why this applies to Zileuton

Zileuton falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group Ipriflavone interacts with.

Ipriflavone is thought to competitively inhibit cytochrome P450 1A2 (CYP1A2). Theoretically, concurrent use of ipriflavone and drugs metabolized by these enzymes might result in decreased drug elimination, increased serum levels, and potential toxicity. Some drugs metabolized by CYP1A2 include clozapine (Clozaril), cyclobenzaprine (Flexeril), fluvoxamine (Luvox), haloperidol (Haldol), imipramine (Tofranil), mexiletine (Mexitil), olanzapine (Zyprexa), Pentazocine (Talwin), propranolol (Inderal), tacrine (Cognex), theophylline (Slo-bid, Theo-Dur, others), zileuton (Zyflo), Zolmitriptan (Zomig), and others.
Severity Moderate Likelihood Possible Evidence D

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.

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

Here's the situation with these two. Your body partly uses an enzyme called CYP1A2 to clear zileuton out of your system. Ipriflavone is thought to slow that same enzyme down, so in theory zileuton could leave your body more slowly and build up to higher levels than usual.

If that happened, you might notice more of zileuton's typical effects, like nausea, stomach upset, headache, or, less commonly, signs that your liver is unhappy (zileuton already requires liver enzyme monitoring). I want to be honest though: this concern comes only from lab studies, not from real-world reports in people, so it's more theoretical than proven. Still, since both can affect the liver, it's worth a quick chat with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Monostory K, Vereczkey L, Levai F, et al. Ipriflavone as an inhibitor of human cytochrome P450 enzymes. Br J Pharmacol 1998;123:605-10. PubMed
Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 2

Zileuton also falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES.

Ipriflavone is thought to competitively inhibit cytochrome P450 2C9 (CYP2C9). Theoretically, concurrent use of ipriflavone and drugs metabolized by these enzymes might result in decreased drug elimination, increased serum levels, and potential toxicity. Some drugs metabolized by CYP2C9 include amitriptyline (Elavil), diazepam (Valium), estradiol (Estrace), tacrine (Cognex), verapamil (Calan), warfarin (Coumadin), zileuton (Zyflo), and others.
Severity Moderate Likelihood Possible Evidence D

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.

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

Here's the gist for your asthma medication. Zileuton is cleared from your body partly by a liver enzyme called CYP2C9, and ipriflavone is thought to slow that enzyme down. If the enzyme works slower, zileuton can clear out less easily, so levels in your blood may creep up a bit. That could mean a higher chance of zileuton's usual side effects, like nausea, upset stomach, headache, or stress on the liver.

I want to keep this in perspective, though. This concern comes only from lab-type testing, not from real people, so it's more theoretical than proven. Still, since zileuton already needs liver monitoring, it's worth a quick chat with your pharmacist or doctor before pairing these two, rather than making any changes on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Monostory K, Vereczkey L, Levai F, et al. Ipriflavone as an inhibitor of human cytochrome P450 enzymes. Br J Pharmacol 1998;123:605-10. 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

Ipriflavone Also Interacts With Other Medications

Ipriflavone has 390 moderate known drug interactions in our database — the Zileuton one above is among them. If you take anything else, check it against the full list below.

Moderate 390 No known interaction 2,440 (incl. Zileuton)
Taking anything else?

Check Another of Your Medications Against Ipriflavone

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

Everything else you take

See Every Supplement That Interacts With Zileuton

This page covers Ipriflavone only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zileuton page lists 213 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 163 moderate · 44 minor.

Open the Zileuton interaction page

One more smart check

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

We hold 204 real supplement products containing Ipriflavone, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ipriflavone. Your product may carry other ingredients that interact with Zileuton too, on top of Ipriflavone — 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 Ipriflavone and Zileuton 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 Ipriflavone
Top half

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

29 days ago today
Medication Zileuton
Steady interest

#1,580 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 Ipriflavone

What is Ipriflavone?

Ipriflavone
  • Bone density and osteoporosis
  • Postmenopausal bone loss
  • Athletic performance
  • Tinnitus related to bone disorders

Ipriflavone is a synthetic isoflavone studied mainly for bone health and osteoporosis, but high-quality research has not shown that it reliably prevents fractures or builds strong bone. Because it can lower white blood cell counts in some people and its long-term safety is not well established, talk with your pharmacist or doctor before using it.

Read the full Ipriflavone monograph & all interactions
Medication

About Zileuton

What Is Zileuton Used For?

Brand names: Zyflo, Zyflo CR

Zileuton is used for the ongoing prevention and treatment of asthma in adults and adolescents aged 12 and older. It is a maintenance medicine — meaning it is taken regularly to keep asthma under control, not to stop an asthma attack once it has started.

Zyflo (the tablet form) and zileuton extended-release tablets are both approved for this same purpose. Neither form should be used to treat a sudden asthma attack. However, both can be continued during a flare-up of asthma while you also use your rescue inhaler.

See full Zileuton drug information
Keep checking

Other Drugs & Ipriflavone

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

0Major
390Moderate
0Minor
2,439No known interaction
390 Moderate 2,439 No interaction
Moderate

390 interactions

Showing 60 of 390 moderate interactions — see all 390 on the Ipriflavone page.

No interaction 2,439 drugs checked — show the list

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

Showing the 60 most looked-up of 2,439 medications checked with no known interaction — see the full Ipriflavone list.

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

Can you take Ipriflavone with Zileuton?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Ipriflavone and Zileuton?
Zileuton belongs to more than one drug category, and Ipriflavone 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 Ipriflavone and Zileuton interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Zileuton and Ipriflavone?

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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.