Medication interaction hub

What Supplements Interact with Fosphenytoin?

Fosphenytoin brand name: Cerebyx. Every interaction below applies to the brands too.

205 Interactions 14 Major 172 Moderate 19 Minor
Curated & coded by · Clinical Pharmacist · Updated September 22, 2026

Drug–supplement interaction data sourced from Natural Medicines Pro, the licensed clinical database from TRC Healthcare / Therapeutic Research, with additional analysis by the HelloPharmacist Pharmacist Team. Our sources · Editorial policy

What is this page for?

One answer, for one medication: what supplements and herbal products interact with Fosphenytoin? Every vitamin, herb, and supplement ingredient we’ve checked against it is on this page, ranked by severity, each linking to the full report for that exact pair.

This page covers supplement interactions only — to check Fosphenytoin against your other medications, use the drug–drug interaction checker. Educational information from our licensed clinical databases, not medical advice. Our editorial policy

HelloPharmacist Bottom Line
Our Pharmacist Explains
What is this? The interaction data in the HelloPharmacist supplement database is licensed from Natural Medicines Pro by TRC Healthcare (Therapeutic Research). HelloPharmacist pharmacists often add our own analysis and context on top of that licensed data — such as this Bottom Line summary and the notes on individual interaction pages — and any such commentary is noted as ours.

St. John's wort is the entry I would flag first with fosphenytoin (Cerebyx). It speeds the breakdown of phenytoin, the seizure medicine fosphenytoin becomes in the body, and lower levels can let seizures break through. Alcohol sits close behind, since 78 of the 205 supplements on this list add to fosphenytoin's sedating effects, sometimes dangerously so. With 14 interactions rated major, this is a list that calls for real care, not a quick skim.

The rest of the picture follows a few patterns. Thirty-eight ingredients can strain the liver, 13 can disturb heart rhythm (grapefruit in large amounts among them), and 23 shift phenytoin levels up or down, which matters when your seizure control depends on a steady dose. Most of the 172 moderate and 19 minor entries repeat these same themes at lower intensity. Read the 14 majors first, and ask your pharmacist about anything on them you already take.

— , Clinical Pharmacist · July 18, 2026

Major 14 Moderate 172 Minor 19 No known interaction 1,247

This box checks one ingredient at a time (like turmeric or magnesium). Taking a supplement product with a whole label of ingredients? Search the product instead — we check every ingredient on it ↓

Most Viewed Ingredient Interactions

Fosphenytoin: Top Interactions at a Glance

The Fosphenytoin supplement & herbal interactions people checked most in the last 24 hours, colored by severity. Tap any ingredient to open the full report for that pair.

Showing the 12 highest-ranked of 205 interacting ingredients — plus 1,247 more checked with no known interaction. See the complete ranked list.

Start here

The Most-Checked Fosphenytoin Combinations Today

The Fosphenytoin + supplement pages people viewed most in the last 24 hours (resets at midnight). Open any card for the full report.

Moderate Likelihood Possible Glutamine + Fosphenytoini

Theoretically, glutamine might antagonize the effects of anticonvulsant medications.

Read the full interaction Moderate Likelihood Possible Black Seed + Fosphenytoini

Theoretically, concomitant use with drugs that have sedative properties may cause additive effects.

Read the full interaction Minor Likelihood Possible Turkey Tail Mushroom + Fosphenytoini

Theoretically, the polysaccharide peptide (PSP) component of turkey tail mushroom might inhibit CYP2C9.

Read the full interaction Moderate Likelihood Possible Dusty Miller + Fosphenytoini

Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid (PA) constituents in dusty miller.

Read the full interaction Major Likelihood Likely Beer + Fosphenytoini

Concomitant use may increase sedative and other adverse effects.

Read the full interaction Major Likelihood Likely Siberian Cocklebur + Fosphenytoini

Siberian cocklebur can adversely affect the liver.

Read the full interaction
The complete list

Every Supplement Checked Against Fosphenytoin

All 1,452 ingredients in our database, ranked by severity — 205 with a Fosphenytoin interaction on file and 1,247 with none found. Filter by severity or search any ingredient; hover the for what each ingredient is.

Looking for an interaction with a specific supplement product? Search products instead ↓

Straight answers

Can You Take It With Fosphenytoin?

One-line answers, one card per combination — scroll through today’s 20 and tap any card for the full report. A different set rotates in daily until every combination has had its turn.

Can you take Glutamine with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, glutamine might antagonize the effects of anticonvulsant medications.

Full Glutamine + Fosphenytoin answer

Can you take Black Seed with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, concomitant use with drugs that have sedative properties may cause additive effects.

Full Black Seed + Fosphenytoin answer

Can you take Turkey Tail Mushroom with Fosphenytoin?

Minor Usually — this is a minor-rated interaction, generally not clinically significant but worth mentioning to your pharmacist. Theoretically, the polysaccharide peptide (PSP) component of turkey tail mushroom might inhibit CYP2C9.

Full Turkey Tail Mushroom + Fosphenytoin answer

Can you take Dusty Miller with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid (PA) constituents in dusty miller.

Full Dusty Miller + Fosphenytoin answer

Can you take Wine with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Concomitant use may increase sedative and other adverse effects.

Full Wine + Fosphenytoin answer

Can you take 1,4-butanediol with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Theoretically, concomitant use of 1,4-butanediol with CNS depressants may potentiate respiratory and CNS depression.

Full 1,4-butanediol + Fosphenytoin answer

Can you take Arsenic with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Arsenic trioxide can prolong the QT interval.

Full Arsenic + Fosphenytoin answer

Can you take Cesium with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Theoretically, taking cesium concomitantly with other drugs that prolong the QT interval may increase the risk of ventricular arrhythmias an...

Full Cesium + Fosphenytoin answer

Can you take Ephedra with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Theoretically, ephedra might have an additive effect with drugs that prolong the QT interval.

Full Ephedra + Fosphenytoin answer

Can you take Gamma-hydroxybutyrate (ghb) with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. GHB may increase the risk of serious CNS and respiratory depression.

Full Gamma-hydroxybutyrate (ghb) + Fosphenytoin answer

Can you take Grapefruit with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Grapefruit or grapefruit juice, especially if consumed in large amounts, can cause additive QT interval prolongation when taken with QT inte...

Full Grapefruit + Fosphenytoin answer

Can you take Kava with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Combining kava with CNS depressants can have additive sedative effects.

Full Kava + Fosphenytoin answer

Can you take L-tryptophan with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.

Full L-tryptophan + Fosphenytoin answer

Can you take Sida Cordifolia with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. Theoretically, Sida cordifolia might increase the risk of additive QT interval prolongation when taken with QT interval-prolonging drugs.

Full Sida Cordifolia + Fosphenytoin answer

Can you take American Hellebore with Fosphenytoin?

Major Use real caution — this is a major-rated interaction, generally best avoided or used only under close supervision. American hellebore, also known as Veratrum viride, contains alkaloids that can potentially prolong the QT interval on an electrocardiogram (...

Full American Hellebore + Fosphenytoin answer

Can you take Cannabidiol (cbd) with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Cannabidiol may increase levels of drugs metabolized by CYP2C9.

Full Cannabidiol (cbd) + Fosphenytoin answer

Can you take Folic Acid with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Folic acid might reduce serum levels of phenytoin in some patients.

Full Folic Acid + Fosphenytoin answer

Can you take Peony with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, peony might reduce the levels and clinical effects of phenytoin.

Full Peony + Fosphenytoin answer

Can you take Yerba Mansa with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, concomitant use might cause additive or prolonged sedative effects.

Full Yerba Mansa + Fosphenytoin answer

Can you take 5-htp with Fosphenytoin?

Moderate Possibly, but carefully — this moderate-rated combination may need monitoring, a dose adjustment, or separated timing. Theoretically, concomitant use of 5-HTP with medications that cause sedation might have additive effects.

Full 5-htp + Fosphenytoin answer
Read the list like a pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction 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.
  • Possible. 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
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each entry links to a full report with the clinical detail, likelihood, evidence level, and citations for that exact combination.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

How Does Our Interaction Checker Work?

Behind every verdict on this page is a category system. Our source database doesn’t document supplement interactions drug-by-drug — it documents them against groups of medications that behave the same way (for example, “drugs processed by the CYP3A4 liver enzyme” or “blood-thinning medications”).

So the check works in three steps: (1) Fosphenytoin is classified into the pharmacology categories it belongs to, (2) every supplement interaction documented against any of those categories is inherited by Fosphenytoin, and (3) each ingredient keeps its own severity, likelihood, and evidence grades from the underlying record. That’s why one supplement can carry several records for one drug — it may interact through more than one category.

Fosphenytoin sits in 11 interaction categories. Open any one to see what the group means:

Cns Depressants 78 ingredients

Central-nervous-system depressants. Sedating supplements can intensify drowsiness and slowed reactions when combined.

78 of the supplement ingredients on this page reach Fosphenytoin through this category.

Cytochrome P450 2C9 (Cyp2C9) Substrates 64 ingredients

A drug-metabolism group: these medications are processed by the named liver enzyme (a cytochrome P450). Supplements that speed this enzyme up or slow it down can lower or raise the medication's levels in your body.

64 of the supplement ingredients on this page reach Fosphenytoin through this category.

Hepatotoxic Drugs 38 ingredients

Medications with known liver considerations. Supplements that can stress the liver add to the load.

38 of the supplement ingredients on this page reach Fosphenytoin through this category.

Phenytoin (Dilantin) 23 ingredients

A pharmacology grouping from our source database: medications in this group share a property that certain supplements are known to interact with, so an interaction documented for the group applies to every drug in it.

23 of the supplement ingredients on this page reach Fosphenytoin through this category.

Cytochrome P450 3A4 (Cyp3A4) Inducers 19 ingredients

A drug-metabolism group: these medications are processed by the named liver enzyme (a cytochrome P450). Supplements that speed this enzyme up or slow it down can lower or raise the medication's levels in your body.

19 of the supplement ingredients on this page reach Fosphenytoin through this category.

Anticonvulsants 15 ingredients

A pharmacology grouping from our source database: medications in this group share a property that certain supplements are known to interact with, so an interaction documented for the group applies to every drug in it.

15 of the supplement ingredients on this page reach Fosphenytoin through this category.

Qt Interval-Prolonging Drugs 13 ingredients

Medications that can affect the heart's electrical rhythm (the QT interval). Supplements with similar effects can add to that risk.

13 of the supplement ingredients on this page reach Fosphenytoin through this category.

Cytochrome P450 2C9 (Cyp2C9) Inducers 3 ingredients

A drug-metabolism group: these medications are processed by the named liver enzyme (a cytochrome P450). Supplements that speed this enzyme up or slow it down can lower or raise the medication's levels in your body.

3 of the supplement ingredients on this page reach Fosphenytoin through this category.

Cytochrome P450 2C19 (Cyp2C19) Inducers 2 ingredients

A drug-metabolism group: these medications are processed by the named liver enzyme (a cytochrome P450). Supplements that speed this enzyme up or slow it down can lower or raise the medication's levels in your body.

2 of the supplement ingredients on this page reach Fosphenytoin through this category.

Cytochrome P450 1A2 (Cyp1A2) Inducers 1 ingredient

A drug-metabolism group: these medications are processed by the named liver enzyme (a cytochrome P450). Supplements that speed this enzyme up or slow it down can lower or raise the medication's levels in your body.

1 of the supplement ingredient on this page reaches Fosphenytoin through this category.

Phenytoin (Dilantin) 1 ingredient

A pharmacology grouping from our source database: medications in this group share a property that certain supplements are known to interact with, so an interaction documented for the group applies to every drug in it.

1 of the supplement ingredient on this page reaches Fosphenytoin through this category.

About Fosphenytoin

Fosphenytoin is an injectable anticonvulsant used to treat or prevent seizures, including generalized tonic-clonic status epilepticus and seizures related to neurosurgery.

Generic name: Fosphenytoin  ·  Brand name: Cerebyx.

See the full Fosphenytoin Injection drug information

Related: does Fosphenytoin deplete any nutrients?

Fosphenytoin has 1 reported nutrient association in the research literature — see the Fosphenytoin nutrient depletion report.

Check a real product

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Most supplements are combination products — and the interaction may come from an ingredient you didn’t buy it for. Search any product below (or scan its label) and we’ll check every ingredient on it against Fosphenytoin.

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Pharmacist Counseling Corner

Fosphenytoin & Supplements: Common Questions

What supplements interact with Fosphenytoin?
More than you might expect — 205 in total, though they are far from equal: 14 are rated major, 172 moderate, and 19 minor. The ranked list on this page puts the ones that genuinely matter first, and every entry opens a full report on that exact pair. The highest-ranked right now: Beer, Siberian Cocklebur, St. John's Wort.
Which Fosphenytoin supplement interactions are the most serious?
Focus on the major group: Beer, Siberian Cocklebur, St. John's Wort, Wine and 1,4-butanediol, among others. A major rating means the combination can be clinically significant, not that harm is guaranteed — but it's exactly the kind of thing to run past your pharmacist before your next dose, not after. Jump to the ranked list.
Can I take vitamins or supplements while on Fosphenytoin?
Usually yes — most people on Fosphenytoin can take most supplements. The catch is the exceptions, and they aren't always the exotic ones (St. John's Wort trips up more prescriptions than almost anything sold next to it). Look up each ingredient you actually take in the list above, and treat "no known interaction" as a green-ish light, not a guarantee. Try the label scanner or the interaction checker.
Do brands like Cerebyx have the same supplement interactions as Fosphenytoin?
Yes — Cerebyx all contain Fosphenytoin, so everything on this page applies to them equally. Interactions belong to the active drug, never to the brand on the box; the same is true of generics.
Where do these interaction ratings come from?
Every rating comes from the Natural Medicines database — the same evidence-graded reference pharmacists and hospitals use — and each interaction carries three separate grades: severity (how bad it can be), likelihood (how well it's documented in studies and case reports), and an evidence level. Our pharmacists review the content; we never let an AI decide an interaction. See how to read the ratings and our editorial policy.
Does Fosphenytoin deplete any vitamins or nutrients?
It might — Fosphenytoin has 1 reported nutrient-depletion association in the research literature, which is a different question from interactions: instead of a supplement changing the drug, the drug may lower a nutrient over time. See the Fosphenytoin nutrient depletion report for the specifics and what to discuss with your pharmacist.
What about Fosphenytoin and my other medications?
This page covers Fosphenytoin against supplements and herbal ingredients. Checking Fosphenytoin against your other prescription or OTC medications is a different tool — our drug interaction checker covers that side. Head to the drug–drug interaction checker, or read the full Fosphenytoin Injection drug information.

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

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Sourcing

Where This Data Comes From — and Why You Can Trust It

🧪 Licensed clinical database

Every interaction verdict on this page comes from Natural Medicines Pro (TRC Healthcare / Therapeutic Research) — the same evidence-graded reference used by pharmacists and hospitals. We license this data directly; we do not scrape it, and no AI invents an interaction.

🧑‍⚕️ Pharmacist review

This page is curated and coded by , Clinical Pharmacist, with additional analysis by the HelloPharmacist Pharmacist Team. Editorial commentary is ours; the licensed interaction records are shown as sourced.

🔄 Kept current

Our interaction database refreshes on a weekly cycle, and this page re-checks the live database every time it’s rebuilt — what you see reflects the database as of September 22, 2026.

🔍 Full transparency

How every dataset on this site is sourced, licensed, and updated is documented publicly: our data sources · editorial policy · how we use AI.

Educational information, not medical advice. An interaction being on file does not mean it will happen to you — and absence of one is not proof of safety. Never start or stop a medication or supplement without talking to your pharmacist or doctor.