Drug & supplement interaction

Sage + Fosphenytoin

Fosphenytoin brand name: Cerebyx.

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

Fosphenytoin falls into 3 drug categories that Sage can interact with; the most serious is rated moderate. Theoretically, taking sage might increase the sedative and adverse effects of CNS depressants.

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

Sage and Fosphenytoin

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

Why Are There 3 Interactions?

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

Moderate

CNS DEPRESSANTS

1 of 3

Why this applies to Fosphenytoin

Fosphenytoin falls under CNS DEPRESSANTS — the group Sage interacts with.

Theoretically, taking sage might increase the sedative and adverse effects of CNS depressants.
Some constituents of sage have CNS depressant activity.
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 short version for sage and fosphenytoin (Cerebyx). This is a brain-calming seizure medicine, and certain natural compounds in sage may have a mild calming (sedative) effect of their own. The idea on file is that stacking the two could add up and make you a little more drowsy, dizzy, foggy, or unsteady than the medication alone.

I want to be honest about how soft this evidence is. It comes only from lab and animal studies, so it's theoretical and not something we see proven in real patients. The bit of sage you use to season dinner is very unlikely to matter. Concentrated sage extracts or essential oil are a different story, since high doses can be harmful for other reasons too. Fosphenytoin is a narrow-window drug, so before adding any sage supplement, please run it by your doctor or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Perry NS, Bollen C, Perry EK, Ballard C. Salvia for dementia therapy: review of pharmacological activity and pilot tolerability clinical trial. Pharmacol Biochem Behav 2003;75:651-9.. PubMed
Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 3

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

Theoretically, sage might increase the levels and clinical effects of drugs metabolized by CYP2C9.
In vitro evidence suggests that aqueous extracts of sage can inhibit CYP2C9. So far, this interaction has not been reported in humans.
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 sage and fosphenytoin. Once it's in your body, fosphenytoin turns into phenytoin, which your liver clears largely through an enzyme called CYP2C9. In test-tube studies, water-based sage extracts seem to slow that enzyme down. If that happened in a real person, phenytoin could build up and tip into too-high levels, which can cause things like dizziness, unsteady walking, slurred speech, drowsiness, or jerky eye movements.

The important part: this is only lab evidence and has never actually been reported in people. Cooking with sage is very unlikely to matter. Still, phenytoin has a narrow safe range, so before using concentrated sage extracts or oil, check with your doctor or pharmacist, who can watch your levels if needed.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Foster BC, Vandenhoek S, Hana J, et al. In vitro inhibition of human cytochrome P450-mediated metabolism of marker substrates by natural products. Phytomedicine 2003;10:334-42.. PubMed
Moderate

ANTICONVULSANTS

3 of 3

Fosphenytoin also falls under ANTICONVULSANTS.

Theoretically, sage might interfere with the clinical effects of anticonvulsant drugs.
Some species of sage can cause convulsions when consumed in large quantities.
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: fosphenytoin (Cerebyx) is a seizure medicine, and sage may work against it. The concern is mostly theoretical and comes from lab and animal data, not strong human studies. Certain sage species, especially concentrated extracts and the essential oil, contain thujone, a compound that in large amounts can actually lower the seizure threshold and possibly trigger convulsions. That could push back against the very effect fosphenytoin is trying to provide, raising the worry of breakthrough seizures.

The good news: sage as a kitchen herb in normal food amounts is very unlikely to cause trouble. It's the concentrated supplements and oils I'd be cautious with. Since seizure control is so important, please check with your doctor or pharmacist before using any sage supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Perry NB, Anderson RE, Brennan NJ, et al. Essential oils from dalmatian sage (Salvia officinalis l.): variations among individuals, plant parts, seasons, and sites. J Agric Food Chem 1999;47:2048-54..

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

Sage Also Interacts With Other Medications

Sage has 1,295 moderate known drug interactions in our database — the Fosphenytoin one above is among them. If you take anything else, check it against the full list below.

Moderate 1,295 No known interaction 1,535 (incl. Fosphenytoin)
Taking anything else?

Check Another of Your Medications Against Sage

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

Everything else you take

See Every Supplement That Interacts With Fosphenytoin

This page covers Sage only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fosphenytoin page lists 205 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 14 major · 172 moderate · 19 minor.

From our pharmacist’s overview on the Fosphenytoin page

“St. John's wort is the entry I would flag first with fosphenytoin (Cerebyx).”

Reviewed by 2 · Jul 18, 2026

Open the Fosphenytoin interaction page

One more smart check

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

We hold 718 real supplement products containing Sage, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Sage. Your product may carry other ingredients that interact with Fosphenytoin too, on top of Sage — 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 Sage and Fosphenytoin 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 Sage
Top 25%

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

29 days ago today
Medication Fosphenytoin
Steady interest

#2,153 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 Sage

What is Sage?

Sage
  • Sore throat and mouth irritation
  • Digestive upset
  • Excessive sweating
  • Memory and thinking
  • Menopause symptoms (hot flashes)
  • General antioxidant support

Sage is a common kitchen herb that is generally safe in food amounts and is traditionally used for sore throats, digestion, sweating, and memory. Some early research is encouraging for sore throat and menopausal hot flashes, but most uses are not well proven. Concentrated extracts and the essential oil should be used carefully because high doses contain a compound called thujone, which can be harmful.

Read the full Sage monograph & all interactions
Medication

About Fosphenytoin Injection

What Is Fosphenytoin Injection Used For?

Brand name: Cerebyx

Fosphenytoin injection is used to treat generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and to prevent or treat seizures that occur during or after brain surgery. It is given by intravenous (IV) or intramuscular (IM) injection in a hospital or clinical setting.

It can also be used short-term as a substitute for oral phenytoin when a patient cannot take medicine by mouth. This use is temporary — as soon as oral phenytoin is possible again, it should replace the injection.

See full Fosphenytoin Injection drug information
Keep checking

Other Drugs & Sage

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

0Major
1,295Moderate
0Minor
1,534No known interaction
1,295 Moderate 1,534 No interaction
Moderate

1,295 interactions

Showing 60 of 1,295 moderate interactions — see all 1,295 on the Sage page.

No interaction 1,534 drugs checked — show the list

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

Showing the 60 most looked-up of 1,534 medications checked with no known interaction — see the full Sage list.

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

Can you take Sage with Fosphenytoin?
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 3 interactions listed for Sage and Fosphenytoin?
Fosphenytoin belongs to more than one drug category, and Sage 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 Sage and Fosphenytoin 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 Fosphenytoin and Sage?

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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.