Drug & supplement interaction

Fo-ti + Hyoscyamine, Phenobarbital

Hyoscyamine, Phenobarbital brand names: Levsin Pb, Levsinex Pb Timecaps.

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

Fo-ti has a moderate interaction with Hyoscyamine, Phenobarbital. Theoretically, fo-ti might increase the levels and clinical effects of drugs metabolized by CYP2B6.

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

Fo-ti and Hyoscyamine, Phenobarbital

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

Moderate

CYTOCHROME P450 2B6 (CYP2B6) SUBSTRATES

Why this applies to Hyoscyamine, Phenobarbital

Hyoscyamine, Phenobarbital falls under CYTOCHROME P450 2B6 (CYP2B6) SUBSTRATES — the group Fo-ti interacts with.

Theoretically, fo-ti might increase the levels and clinical effects of drugs metabolized by CYP2B6.
Animal research suggests that fo-ti might inhibit CYP2B6. One in vitro study suggests that the degree of CYP2B6 inhibition may depend on the type of fo-ti extract (i.e., the raw plant leads to greater inhibition than extensively processed extracts). However, 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

This combination product pairs hyoscyamine with phenobarbital. The piece that matters here is the phenobarbital, which your liver clears partly through an enzyme called CYP2B6. Lab and animal studies hint that Fo-ti, especially the raw root, might slow that enzyme down. If it did, phenobarbital could build up a bit, and since it's a sedative with a fairly narrow safety window, that could mean extra drowsiness, dizziness, grogginess, or feeling unsteady.

I want to be honest about how shaky this evidence is. This has only been seen in test tubes and animals, never confirmed in people, so it may not amount to much in real life. Still, because phenobarbital is a drug where small shifts can matter, I'd run the idea of adding Fo-ti past your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zhang Y, Ding T, Diao T, Deng M, Chen S. Effects of Polygonum multiflorum on the activity of cytochrome P450 isoforms in rats. Pharmazie 2015;70(1):47-54. DOI
  2. Xing Y, Yu Q, Zhou L, et al. Cytochrome P450-mediated herb-drug interaction (HDI) of Polygonum multiflorum Thunb. based on pharmacokinetic studies and in vitro inhibition assays. Phytomedicine 2023;112:154710. 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

Fo-ti Also Interacts With Other Medications

Fo-ti has 1,256 moderate known drug interactions in our database — the Hyoscyamine, Phenobarbital one above is one of them. If you take anything else, check it against the full list below.

Moderate 1,256 No known interaction 1,574 (incl. Hyoscyamine, Phenobarbital)
Taking anything else?

Check Another of Your Medications Against Fo-ti

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

Everything else you take

See Every Supplement That Interacts With Hyoscyamine, Phenobarbital

This page covers Fo-ti only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hyoscyamine, Phenobarbital page lists 164 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 Henbane (major).

By severity: 10 major · 134 moderate · 20 minor.

From our pharmacist’s overview on the Hyoscyamine, Phenobarbital page

“The person taking Levsin PB (hyoscyamine with phenobarbital) for gut spasms is often the same person browsing calming herbs and sleep aids, and with this medicine that habit calls for real vigilance. Ten of the 164 supplements on record rate major, and the largest group, 78 ingredients, shares one danger.”

Reviewed by 2 · Jul 18, 2026

Open the Hyoscyamine, Phenobarbital interaction page

One more smart check

Taking Fo-ti as Part of a Dietary Supplement Product? Check It for Interactions

We hold 976 real supplement products containing Fo-ti, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fo-ti. Your product may carry other ingredients that interact with Hyoscyamine, Phenobarbital too, on top of Fo-ti — 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 Fo-ti and Hyoscyamine, Phenobarbital 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 Fo-ti
Top 25%

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

29 days ago today
Medication Hyoscyamine, Phenobarbital
Top half

#1,376 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 Fo-ti

What is Fo-ti?

  • Anti-aging and longevity
  • Hair graying and hair loss
  • General tonic for vitality
  • Constipation
  • High cholesterol

Fo-ti (He Shou Wu) is a root used in traditional Chinese medicine, often promoted for healthy aging and hair. High-quality human evidence for these benefits is limited, and processed Fo-ti has been linked to reports of liver injury, so caution and professional guidance are important.

Read the full Fo-ti monograph & all interactions
Keep checking

Other Drugs & Fo-ti

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

0Major
1,256Moderate
0Minor
1,573No known interaction
1,256 Moderate 1,573 No interaction
Moderate

1,256 interactions

Showing 60 of 1,256 moderate interactions — see all 1,256 on the Fo-ti page.

No interaction 1,573 drugs checked — show the list

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

Showing the 60 most looked-up of 1,573 medications checked with no known interaction — see the full Fo-ti list.

See the full Fo-ti interactions page
See every supplement checked against Hyoscyamine, Phenobarbital, 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
Fo-ti monograph › Uses, safety, and every drug interaction in one place Hyoscyamine, Phenobarbital supplement interactions › Every supplement checked against Hyoscyamine, Phenobarbital, 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 Fo-ti and Hyoscyamine, Phenobarbital Together: Common Questions

Can you take Fo-ti with Hyoscyamine, Phenobarbital?
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 Fo-ti and Hyoscyamine, Phenobarbital 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 Hyoscyamine, Phenobarbital and Fo-ti?

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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.