Drug & supplement interaction

Toothed Clubmoss + Donepezil

Donepezil brand name: Aricept.

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

Toothed Clubmoss has a moderate interaction with Donepezil. Huperzine A, a constituent of toothed clubmoss, has demonstrated acetylcholinesterase inhibitory properties.

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

Toothed Clubmoss and Donepezil

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

Moderate

CHOLINERGIC DRUGS

Why this applies to Donepezil

Donepezil falls under CHOLINERGIC DRUGS — the group Toothed Clubmoss interacts with.

Huperzine A, a constituent of toothed clubmoss, has demonstrated acetylcholinesterase inhibitory properties. Theoretically, concurrent use of toothed clubmoss with cholinergic drugs might have additive effects and increase the risk of cholinergic side effects.
Cholinergic drugs include bethanechol (Urecholine), donepezil (Aricept), echothiophate (Phospholine Iodide), edrophonium (Enlon, Reversol, Tensilon), neostigmine (Prostigmin), physostigmine (Antilirium), pyridostigmine (Mestinon, Regonol), succinylcholine (Anectine, Quelicin), and tacrine (Cognex).
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: both donepezil and toothed clubmoss work the same way. Donepezil is a cholinesterase inhibitor, and huperzine A (the active part of toothed clubmoss) does basically the same job. So taking them together is like pressing on the same gas pedal twice. You're not changing how donepezil is broken down, you're just stacking two similar effects.

That means a higher chance of cholinergic side effects: nausea, diarrhea, stomach cramps, a slow heart rate, more drooling or sweating, muscle cramps, or trouble sleeping. To be fair, this caution is theoretical, based on how these compounds work rather than proven cases. Still, since they overlap so much, please check with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Budavari S, ed. The Merck Index. 12th ed. Whitehouse Station, NJ: Merck & Co., Inc., 1996.
  2. Ohba T, Yoshino Y, Ishisaka M, et al. Japanese Huperzia serrata extract and the constituent, huperzine A, ameliorate the scopolamine-induced cognitive impairment in mice. Biosci Biotechnol Biochem. 2015;79(11):1838-44.

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 Donepezil 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. Donepezil)
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 Donepezil

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 Donepezil, 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 Donepezil

This page covers Toothed Clubmoss only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Donepezil page lists 173 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 1,3-dmaa (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 127 moderate · 43 minor.

From our pharmacist’s overview on the Donepezil page

“If you or a loved one takes donepezil (Aricept) for Alzheimer's disease, this is a list worth reading with real care, starting with the three major-rated entries: grapefruit, St. John's wort, and activated charcoal.”

Reviewed by 2 · Jul 18, 2026

Open the Donepezil 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 Donepezil 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 Donepezil 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

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

29 days ago today
Medication Donepezil
Steady interest

#1,604 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 Donepezil

What Is Donepezil Used For?

Brand name: Aricept

Donepezil is used to treat dementia of the Alzheimer's type. It has been shown to be effective across all stages — mild, moderate, and severe Alzheimer's disease.

It can help with memory, thinking, and daily functioning, though it works differently for each person. Donepezil does not cure Alzheimer's disease or stop the disease from progressing.

See full Donepezil 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 Donepezil, 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 Donepezil supplement interactions › Every supplement checked against Donepezil, ranked by severity Donepezil 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 Donepezil Together: Common Questions

Can you take Toothed Clubmoss with Donepezil?
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 Donepezil 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 Donepezil 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.