Drug & supplement interaction

Borage + Fosphenytoin Sodium

Fosphenytoin Sodium brand name: Sesquient.

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

Borage has a moderate interaction with Fosphenytoin Sodium. Theoretically, taking borage with drugs that induce CYP3A4 might increase levels of pyrrolizidine alkaloid (PA) toxic metabolites.

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

Borage and Fosphenytoin Sodium

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) INDUCERS

Why this applies to Fosphenytoin Sodium

Fosphenytoin Sodium falls under CYTOCHROME P450 3A4 (CYP3A4) INDUCERS — the group Borage interacts with.

Theoretically, taking borage with drugs that induce CYP3A4 might increase levels of pyrrolizidine alkaloid (PA) toxic metabolites.
Although borage seed oil contains little to no PAs, some borage plant parts, such as the leaf, flower, and seed, can contain hepatotoxic PAs. Hepatotoxic PAs are substrates of CYP3A4, which converts these chemicals into toxic metabolites. Tell patients to avoid borage preparations that are not certified and labeled as hepatotoxic PA-free.
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 angle that matters with this pairing. Fosphenytoin (Sesquient) is a strong inducer of a liver enzyme called CYP3A4, meaning it revs that enzyme up. Borage leaf, flower, and seed can carry natural compounds called pyrrolizidine alkaloids (PAs), and CYP3A4 is exactly what turns those PAs into liver-damaging byproducts. So in theory, fosphenytoin could speed up the creation of those harmful metabolites and raise the risk of liver injury (think fatigue, nausea, belly pain on the right side, or yellowing skin or eyes).

Keep in mind this is a theoretical concern based on lab data, not strong human studies, and properly made PA-free borage seed oil contains little to no PAs. The safest move is to only use products clearly labeled PA-free, and check with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
  2. Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. 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

Borage Also Interacts With Other Medications

Borage has 225 moderate known drug interactions in our database — the Fosphenytoin Sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 225 No known interaction 2,605 (incl. Fosphenytoin Sodium)
Taking anything else?

Check Another of Your Medications Against Borage

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

Everything else you take

See Every Supplement That Interacts With Fosphenytoin Sodium

This page covers Borage only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fosphenytoin Sodium page lists 212 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 · 179 moderate · 19 minor.

From our pharmacist’s overview on the Fosphenytoin Sodium page

“Fosphenytoin sodium (Sesquient) converts to phenytoin in the body, and phenytoin is unforgiving about blood levels. A little too low invites seizures, a little too high brings toxicity.”

Reviewed by 2 · Jul 18, 2026

Open the Fosphenytoin Sodium interaction page

One more smart check

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

We hold 122 real supplement products containing Borage, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Borage. Your product may carry other ingredients that interact with Fosphenytoin Sodium too, on top of Borage — 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 Borage and Fosphenytoin Sodium 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 Borage
Top 25%

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

29 days ago today
Medication Fosphenytoin Sodium
Steady interest

#1,613 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 Borage

What is Borage?

Borage
  • Eczema and dry skin
  • Rheumatoid arthritis
  • Inflammation
  • Respiratory complaints
  • Mood and stress

Borage is a Mediterranean herb whose seed oil is rich in gamma-linolenic acid (GLA), an omega-6 fatty acid studied mostly for skin conditions and arthritis with mixed results. The plant's leaves and flowers can contain liver-toxic pyrrolizidine alkaloids, so only use products clearly labeled 'PA-free' and talk to your pharmacist or doctor before taking it.

Read the full Borage monograph & all interactions
Keep checking

Other Drugs & Borage

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

0Major
225Moderate
0Minor
2,604No known interaction
225 Moderate 2,604 No interaction
Moderate

225 interactions

Showing 60 of 225 moderate interactions — see all 225 on the Borage page.

No interaction 2,604 drugs checked — show the list

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

Showing the 60 most looked-up of 2,604 medications checked with no known interaction — see the full Borage list.

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

Can you take Borage with Fosphenytoin Sodium?
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 Borage and Fosphenytoin Sodium 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

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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.