Drug & supplement interaction

Coleus + Phenytoin

Phenytoin brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, and others.

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

Coleus has a moderate interaction with Phenytoin. Theoretically, taking coleus may affect drugs metabolized by CYP2C9 and increase the risk of adverse effects or reduce the effectiveness.

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

Coleus and Phenytoin

Here is the interaction we found between these two, with the evidence behind it.

Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

Why this applies to Phenytoin

Phenytoin falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Coleus interacts with.

Theoretically, taking coleus may affect drugs metabolized by CYP2C9 and increase the risk of adverse effects or reduce the effectiveness.
Research on the effect of coleus on CYP2C9 is conflicting. Some animal research shows that coleus extract can induce CYP2C9, while in vitro research shows that coleus can inhibit CYP2C9. Until more is known, advise patients that taking coleus might increase or decrease levels of drugs metabolized by CYP2C9.
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 thing about phenytoin (Dilantin): your liver clears it largely through an enzyme called CYP2C9, and phenytoin is one of those medicines with a narrow safety window. Small shifts in its blood level can tip you toward too little (breakthrough seizures) or too much (dizziness, slurred speech, wobbly walking, double vision, or nausea).

Coleus (forskolin) might nudge this enzyme, but honestly the science is a mess. Some animal studies suggest it speeds the enzyme up (which could lower your level), while lab dish studies suggest it slows it down (which could raise your level). This is theoretical and based only on lab and animal work, so don't panic. Still, because phenytoin is so dose-sensitive, please check with your pharmacist or doctor before adding Coleus.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Yokotani K, Chiba T, Sato Y, et al. Hepatic cytochrome P450 mediates interaction between warfarin and Coleus forskohlii extract in vivo and in vitro. J Pharm Pharmacol. 2012;64(12):1793-801.

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

Coleus Also Interacts With Other Medications

Coleus has 29 major, 885 moderate known drug interactions in our database — the Phenytoin one above is one of them. If you take anything else, check it against the full list below.

Major 29 Moderate 885 No known interaction 1,916 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Coleus

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

From our Q&A

Questions About Coleus or Phenytoin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Coleus or Phenytoin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenytoin

This page covers Coleus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenytoin page lists 224 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 187 moderate · 28 minor.

From our pharmacist’s overview on the Phenytoin page

“Phenytoin (Dilantin) is a seizure medicine with a narrow therapeutic index, meaning small changes in its blood level can bring seizures back or tip over into toxicity, so I treat its supplement list with real seriousness. The biggest group, 78 ingredients, piles on sedation, and alcohol, kava, and GHB all rate major for exactly that re…”

Reviewed by 2 · Jul 18, 2026

Open the Phenytoin interaction page

One more smart check

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

We hold 803 real supplement products containing Coleus, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Coleus. Your product may carry other ingredients that interact with Phenytoin too, on top of Coleus — 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 Coleus and Phenytoin 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 Coleus
Top 25%

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

29 days ago today
Medication Phenytoin
Steady interest

#1,739 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 Coleus

What is Coleus?

Coleus
  • Weight management
  • Asthma and breathing
  • High blood pressure
  • Heart conditions
  • Glaucoma (eye pressure)
  • Exercise and body composition

Coleus is a plant from the mint family whose root contains a compound called forskolin, often marketed for weight loss, asthma, and heart health. While early lab and small human studies are interesting, solid proof that Coleus supplements help any of these conditions is limited. Talk to your pharmacist or doctor before using it, especially if you have heart problems or low blood pressure.

Read the full Coleus monograph & all interactions
Medication

About Phenytoin

What Is Phenytoin Used For?

Brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, Dilantin injection

Phenytoin is used to treat and prevent seizures. The specific types covered depend on the formulation. Oral extended-release capsules (including Phenytek), chewable tablets (including Dilantin Infatabs and Phenytoin Infatabs), and oral suspension (including Dilantin-125) are used for tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; most oral forms also cover prevention and treatment of seizures occurring during or after neurosurgery. Chewable tablets and some capsule formulations also cover complex partial seizures.

Parenteral (injectable) phenytoin sodium is used for generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and for prevention and treatment of seizures during neurosurgery. The IV form can also substitute short-term for oral phenytoin when a patient cannot take it by mouth.

See full Phenytoin drug information
Keep checking

Other Drugs & Coleus

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

29Major
885Moderate
0Minor
1,915No known interaction
29 Major 885 Moderate 1,915 No interaction
Major

29 interactions

Moderate

885 interactions

Showing 60 of 885 moderate interactions — see all 885 on the Coleus page.

No interaction 1,915 drugs checked — show the list

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

Showing the 60 most looked-up of 1,915 medications checked with no known interaction — see the full Coleus list.

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

Can you take Coleus with Phenytoin?
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.
How serious is the Coleus and Phenytoin 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 Phenytoin and Coleus?

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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.