Drug & supplement interaction

Toothed Clubmoss + Hydroxyzine

Hydroxyzine brand names: Atarax, Vistaril, Ucerax.

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

Toothed Clubmoss has a moderate interaction with Hydroxyzine. In animal models, toothed clubmoss and huperzine A, an active constituent of toothed clubmoss, reversed cognitive deficits induced by scopolamine.

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

Toothed Clubmoss and Hydroxyzine

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

Moderate

ANTICHOLINERGIC DRUGS

Why this applies to Hydroxyzine

Hydroxyzine falls under ANTICHOLINERGIC DRUGS — the group Toothed Clubmoss interacts with.

In animal models, toothed clubmoss and huperzine A, an active constituent of toothed clubmoss, reversed cognitive deficits induced by scopolamine. Theoretically, concurrent use of anticholinergic drugs and toothed clubmoss might decrease the effectiveness of toothed clubmoss or the anticholinergic drug.
Some anticholinergic drugs include atropine, benztropine (Cogentin), biperiden (Akineton), procyclidine (Kemadrin), and trihexyphenidyl (Artane).
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 simple version: hydroxyzine has anticholinergic effects, meaning it blocks the brain chemical acetylcholine. Toothed clubmoss (its active part, huperzine A) does the opposite, it raises acetylcholine. So these two work against each other. Used together, each one may partly cancel the other out. Your hydroxyzine could feel a bit less effective for itching or anxiety, and the clubmoss may not work as well either.

I want to be honest about the evidence, though. This concern comes only from animal and lab studies, not from people, so it's mostly theoretical. It's not dangerous so much as a possible loss of benefit. If you take both, mention it to your pharmacist or doctor so they can keep an eye on how well things are working.

Contact Dr. Brian directly if you have additional questions on this interaction

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

Toothed Clubmoss Also Interacts With Other Medications

Toothed Clubmoss has 218 moderate known drug interactions in our database — the Hydroxyzine one above is one of them. If you take anything else, check it against the full list below.

Moderate 218 No known interaction 2,612 (incl. Hydroxyzine)
Taking anything else?

Check Another of Your Medications Against Toothed Clubmoss

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

From our Q&A

Questions About Toothed Clubmoss or Hydroxyzine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Toothed Clubmoss or Hydroxyzine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Hydroxyzine

This page covers Toothed Clubmoss only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydroxyzine page lists 183 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Henbane (major), Scopolia (major) and St. John's Wort (major).

By severity: 5 major · 135 moderate · 43 minor.

From our pharmacist’s overview on the Hydroxyzine page

“Hydroxyzine (Atarax, Vistaril) is a sedating antihistamine for itching and anxiety, so read this list closely before pairing it with any supplement. Five of the 183 ingredients on file rate major, and those come first: grapefruit and St.”

Reviewed by 2 · Jul 18, 2026

Open the Hydroxyzine interaction page

One more smart check

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

We hold 101 real supplement products containing Toothed Clubmoss, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Toothed Clubmoss. Your product may carry other ingredients that interact with Hydroxyzine too, on top of Toothed Clubmoss — 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 Toothed Clubmoss and Hydroxyzine 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 Toothed Clubmoss
Top half

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

29 days ago today
Medication Hydroxyzine
Top 25%

#473 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 Toothed Clubmoss

What is Toothed Clubmoss?

Toothed Clubmoss
  • Memory and cognitive support
  • Alzheimer's disease and dementia
  • General brain or 'nootropic' support
  • Inflammation and pain (traditional use)
  • Age-related memory loss

Toothed Clubmoss is a moss-like plant best known as the natural source of huperzine A, a compound studied mainly for memory and Alzheimer's disease. Some early research is promising, but the evidence is limited and the supplement is not well standardized or regulated, so quality between products varies. Because it can affect the nervous system, talk with a pharmacist or doctor before using it.

Read the full Toothed Clubmoss monograph & all interactions
Medication

About Hydroxyzine

What Is Hydroxyzine Used For?

Brand names: Atarax, Vistaril, Ucerax

Hydroxyzine is used to relieve anxiety and tension related to psychoneurosis (anxiety-based mental health conditions) and as a supportive treatment when anxiety is part of another medical condition. Oral forms — including tablets, capsules, and oral solution — are used for anxiety relief and to manage itching (pruritus) caused by allergic conditions such as chronic urticaria (hives), atopic dermatitis, contact dermatitis, and histamine-driven itch. Oral forms are also used as a sedative before and after surgery or general anesthesia.

Hydroxyzine Hydrochloride intramuscular injection is used specifically when a shot is needed — for example, in acute psychiatric or emotional emergencies, acute alcohol withdrawal with anxiety symptoms or delirium tremens, control of nausea and vomiting (except during pregnancy), and as pre- and post-operative or pre- and post-partum supportive medication to reduce narcotic requirements and control nausea.

See full Hydroxyzine drug information
Keep checking

Other Drugs & Toothed Clubmoss

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

0Major
218Moderate
0Minor
2,611No known interaction
218 Moderate 2,611 No interaction
Moderate

218 interactions

Showing 60 of 218 moderate interactions — see all 218 on the Toothed Clubmoss page.

No interaction 2,611 drugs checked — show the list

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

Showing the 60 most looked-up of 2,611 medications checked with no known interaction — see the full Toothed Clubmoss list.

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

Can you take Toothed Clubmoss with Hydroxyzine?
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 Toothed Clubmoss and Hydroxyzine 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 Hydroxyzine and Toothed Clubmoss?

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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.