Drug & supplement interaction

Baikal Skullcap + Fosphenytoin Sodium

Fosphenytoin Sodium brand name: Sesquient.

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

Fosphenytoin Sodium falls into 2 drug categories that Baikal Skullcap can interact with; the most serious is rated moderate. Theoretically, Baikal skullcap might increase levels of drugs metabolized by CYP2C19 enzymes.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Baikal Skullcap and Fosphenytoin Sodium

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Baikal Skullcap interacts with whole categories of medication. Fosphenytoin Sodium falls into 2 of those categories, so it can interact with Baikal Skullcap in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES

1 of 2

Why this applies to Fosphenytoin Sodium

Fosphenytoin Sodium falls under CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES — the group Baikal Skullcap interacts with.

Theoretically, Baikal skullcap might increase levels of drugs metabolized by CYP2C19 enzymes.
In vitro evidence suggest that wogonin, a constituent of Baikal skullcap, modestly inhibits the activity of CYP2C19 enzymes. This effect 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 short version: once it's in your body, fosphenytoin quickly converts to phenytoin, your active anti-seizure medicine. Phenytoin is partly cleared by a liver enzyme called CYP2C19. A compound in Baikal skullcap (wogonin) has, in lab dishes only, mildly slowed that same enzyme. In theory, that could let phenytoin build up a bit higher than expected.

Why I pay attention here: phenytoin has a narrow safety window, so even small shifts can tip you toward side effects like dizziness, unsteady walking, slurred speech, double vision, or drowsiness. That said, this is only test-tube evidence and hasn't been seen in real patients. Please don't start or stop anything on your own. Just loop in your pharmacist or neurologist first, since they may want to check a phenytoin level.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Li, T., Li, N., Guo, Q., Ji, H., Zhao, D., Xie, S., Li, X., Qiu, Z., Han, D., Chen, X., and You, Q. Inhibitory effects of wogonin on catalytic activity of cytochrome P450 enzyme in human liver microsomes. Eur J Drug Metab Pharmacokinet. 6-29-2011; PubMed
Minor

CNS DEPRESSANTS

2 of 2

Fosphenytoin Sodium also falls under CNS DEPRESSANTS.

Theoretically, Baikal skullcap might cause additive therapeutic and adverse effects when used concomitantly with drugs with sedative properties.
In vitro and animal research suggests that Baikal skullcap binds to GABA-A receptors and causes sedation. Theoretically, Baikal skullcap might cause additive therapeutic and adverse effects when used concomitantly with drugs with sedative properties. Preliminary clinical research has not identified clinically relevant sedation after use of Baikal skullcap; however, a thorough evaluation of safety outcomes has not been conducted.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for fosphenytoin (Sesquient), which your body converts into phenytoin, an anti-seizure medicine that can already make people feel drowsy or unsteady. Baikal skullcap has been shown in test-tube and animal studies to gently nudge the same calming GABA receptors in the brain. So in theory, pairing the two could add up to a little extra drowsiness, dizziness, or feeling foggy.

I want to keep this in perspective, though. This concern comes only from lab and animal research, and early human studies haven't shown meaningful sedation from the herb. So it's a low-level, theoretical worry, not something seen in practice. Since fosphenytoin is a serious medication, just give your pharmacist or doctor a heads-up before adding the supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Hui KM, Wang XH, Xue H. Interaction of flavones from the roots of Scutellaria baicalensis with the benzodiazepine site. Planta Med 2000;66:91-3.
  2. Liao JF, Wang HH, Chen MC, et al. Benzodiazepine binding site-interactive flavones from Scutellaria baicalensis root. Planta Med 1998;64:571-2.
  3. Chang, H. H., Yi, P. L., Cheng, C. H., Lu, C. Y., Hsiao, Y. T., Tsai, Y. F., Li, C. L., and Chang, F. C. Biphasic effects of baicalin, an active constituent of Scutellaria baicalensis Georgi, in the spontaneous sleep-wake regulation. J Ethnopharmacol. 5- 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

Baikal Skullcap Also Interacts With Other Medications

Baikal Skullcap has 594 moderate, 353 minor known drug interactions in our database — the Fosphenytoin Sodium one above is among them. If you take anything else, check it against the full list below.

Moderate 594 Minor 353 No known interaction 1,883 (incl. Fosphenytoin Sodium)
Taking anything else?

Check Another of Your Medications Against Baikal Skullcap

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

Everything else you take

See Every Supplement That Interacts With Fosphenytoin Sodium

This page covers Baikal Skullcap 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 Baikal Skullcap as Part of a Dietary Supplement Product? Check It for Interactions

We hold 737 real supplement products containing Baikal Skullcap, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Baikal Skullcap. Your product may carry other ingredients that interact with Fosphenytoin Sodium too, on top of Baikal Skullcap — 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 Baikal Skullcap 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 Baikal Skullcap
Top 25%

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

29 days ago today
Medication Fosphenytoin Sodium
Top 5%

#114 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 Baikal Skullcap

What is Baikal Skullcap?

Baikal Skullcap
  • Inflammation
  • Allergies
  • Anxiety and sleep
  • Immune support
  • Respiratory infections

Baikal skullcap is a traditional Chinese herb (Huang Qin) used for inflammation, allergies, and infections, with active compounds like baicalin and baicalein studied mostly in the lab. Human evidence remains limited, so it should not replace proven treatments. Talk to your pharmacist or doctor before using it, and avoid it in pregnancy and breastfeeding.

Read the full Baikal Skullcap monograph & all interactions
Keep checking

Other Drugs & Baikal Skullcap

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

0Major
594Moderate
353Minor
1,882No known interaction
594 Moderate 353 Minor 1,882 No interaction
Moderate

594 interactions

Showing 60 of 594 moderate interactions — see all 594 on the Baikal Skullcap page.

Minor

353 interactions

Showing 60 of 353 minor interactions — see all 353 on the Baikal Skullcap page.

No interaction 1,882 drugs checked — show the list

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

Showing the 60 most looked-up of 1,882 medications checked with no known interaction — see the full Baikal Skullcap list.

See the full Baikal Skullcap 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
Baikal Skullcap 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 Baikal Skullcap and Fosphenytoin Sodium Together: Common Questions

Can you take Baikal Skullcap 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.
Why are there 2 interactions listed for Baikal Skullcap and Fosphenytoin Sodium?
Fosphenytoin Sodium belongs to more than one drug category, and Baikal Skullcap 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 Baikal Skullcap 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.