Drug & supplement interaction

Hibiscus Sabdariffa + Phenytoin

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

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

Phenytoin falls into 3 drug categories that Hibiscus Sabdariffa can interact with; the most serious is rated minor. Theoretically, Hibiscus sabdariffa extract might reduce the metabolism of CYP2C19 substrates.

Read the full interaction report
SeverityMinor
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Hibiscus Sabdariffa and Phenytoin

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Hibiscus Sabdariffa interacts with whole categories of medication. Phenytoin falls into 3 of those categories, so it can interact with Hibiscus Sabdariffa in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Minor).

Minor

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES

1 of 3

Why this applies to Phenytoin

Phenytoin falls under CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES — the group Hibiscus Sabdariffa interacts with.

Theoretically, Hibiscus sabdariffa extract might reduce the metabolism of CYP2C19 substrates.
In vitro research shows that Hibiscus sabdariffa calyx extract inhibits CYP2C19. This interaction has not been reported in humans.
Severity Minor 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 with hibiscus and your phenytoin. In lab dish studies, hibiscus extract seems to slow down an enzyme called CYP2C19, which is one of the pathways your body uses to clear phenytoin. If that pathway slows, phenytoin could theoretically build up a bit more than expected. With phenytoin that matters, because it's a narrow therapeutic index drug, meaning the gap between a helpful level and a too-high level is small. Higher levels can show up as dizziness, drowsiness, unsteady walking, slurred speech, or jerky eye movements.

The reassuring part: this is theoretical and has never actually been seen in people. A cup of tart hibiscus tea is unlikely to cause trouble, but concentrated supplements are worth running by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Johnson SS, Oyelola FT, Ari T, Juho H. In vitro inhibitory activities of the extract of Hibiscus sabdariffa L. (family Malvaceae) on selected cytochrome P450 isoforms. Afr J Tradit Complement Altern Med. 2013 Apr 12;10(3):533-40.
Minor

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 3

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

Theoretically, Hibiscus sabdariffa extract might reduce the metabolism of CYP2C9 substrates.
In vitro research shows that Hibiscus sabdariffa calyx extract inhibits CYP2C9. This interaction has not been reported in humans.
Severity Minor 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 with hibiscus and your phenytoin. Your body relies on a liver enzyme called CYP2C9 to break phenytoin down. In lab (test tube) studies, hibiscus extract appears to slow that enzyme a little. If that happened in a real person, phenytoin could clear more slowly and creep upward in your blood. Since phenytoin is a narrow therapeutic index drug, even small shifts can tip you into side effects like dizziness, unsteady walking, slurred speech, double vision, or drowsiness.

The reassuring part: this is only a theory based on lab work and has never actually been seen in people, so I wouldn't lose sleep over an occasional cup of hibiscus tea. Concentrated supplement doses are the bigger question mark. Before adding those, please run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Johnson SS, Oyelola FT, Ari T, Juho H. In vitro inhibitory activities of the extract of Hibiscus sabdariffa L. (family Malvaceae) on selected cytochrome P450 isoforms. Afr J Tradit Complement Altern Med. 2013 Apr 12;10(3):533-40.
Minor

CYTOCHROME P450 2C8 (CYP2C8) SUBSTRATES

3 of 3

Phenytoin also falls under CYTOCHROME P450 2C8 (CYP2C8) SUBSTRATES.

Theoretically, Hibiscus sabdariffa might reduce the metabolism of CYP2C8 substrates.
In vitro research shows that Hibiscus sabdariffa calyx extract inhibits CYP2C8. This interaction has not been reported in humans.
Severity Minor 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 short version: lab tests suggest hibiscus might slow down an enzyme called CYP2C8, which is one of the pathways your body uses to break down phenytoin. In theory, if that pathway is blocked, phenytoin could build up a bit and you might feel more of its side effects, things like dizziness, unsteadiness, slurred speech, drowsiness, or jerky eye movements.

The honest truth is that this concern only comes from test-tube research, and it has never actually been reported in real people. Still, phenytoin is a tricky drug where small blood-level changes can matter, so I wouldn't ignore it. An occasional cup of hibiscus tea is unlikely to be a problem, but concentrated supplements are a bigger question mark. Please run it by your pharmacist or doctor before adding hibiscus regularly.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Johnson SS, Oyelola FT, Ari T, Juho H. In vitro inhibitory activities of the extract of Hibiscus sabdariffa L. (family Malvaceae) on selected cytochrome P450 isoforms. Afr J Tradit Complement Altern Med. 2013 Apr 12;10(3):533-40.

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

Hibiscus Sabdariffa Also Interacts With Other Medications

Hibiscus Sabdariffa has 2 major, 266 moderate, 818 minor known drug interactions in our database — the Phenytoin one above is among them. If you take anything else, check it against the full list below.

Major 2 Moderate 266 Minor 818 No known interaction 1,744 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Hibiscus Sabdariffa

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

From our Q&A

Questions About Hibiscus Sabdariffa 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 Hibiscus Sabdariffa 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 Hibiscus Sabdariffa 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

How much people look this up

Where Hibiscus Sabdariffa 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 Hibiscus Sabdariffa
Top half

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

29 days ago today
Medication Phenytoin
Steady interest

#1,786 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 Hibiscus Sabdariffa

What is Hibiscus Sabdariffa?

Hibiscus Sabdariffa
  • High blood pressure
  • Heart and cholesterol health
  • Digestive upset
  • Antioxidant support
  • Fever and general wellness

Hibiscus sabdariffa is a tart, cranberry-flavored plant most often consumed as a tea, and its best-studied use is for mildly lowering blood pressure. Evidence for other uses is limited, and while hibiscus tea is generally well tolerated in food amounts, concentrated supplements should be used cautiously and avoided in pregnancy. Talk to your pharmacist or doctor before using it for a medical condition.

Read the full Hibiscus Sabdariffa 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 & Hibiscus Sabdariffa

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

2Major
266Moderate
818Minor
1,743No known interaction
2 Major 266 Moderate 818 Minor 1,743 No interaction
Major

2 interactions

Moderate

266 interactions

Showing 60 of 266 moderate interactions — see all 266 on the Hibiscus Sabdariffa page.

Minor

818 interactions

Showing 60 of 818 minor interactions — see all 818 on the Hibiscus Sabdariffa page.

No interaction 1,743 drugs checked — show the list

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

Showing the 60 most looked-up of 1,743 medications checked with no known interaction — see the full Hibiscus Sabdariffa list.

See the full Hibiscus Sabdariffa 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
Hibiscus Sabdariffa 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 Hibiscus Sabdariffa and Phenytoin Together: Common Questions

Can you take Hibiscus Sabdariffa with Phenytoin?
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 3 interactions listed for Hibiscus Sabdariffa and Phenytoin?
Phenytoin belongs to more than one drug category, and Hibiscus Sabdariffa 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 Hibiscus Sabdariffa and Phenytoin 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 Phenytoin and Hibiscus Sabdariffa?

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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.