Drug & supplement interaction

Huperzine A + Doxylamine Succinate

Doxylamine Succinate brand name: Unisom.

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

Huperzine A has a moderate interaction with Doxylamine Succinate. Theoretically, huperzine A might decrease the effects of anticholinergic drugs.

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

Huperzine A and Doxylamine Succinate

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

Moderate

ANTICHOLINERGIC DRUGS

Why this applies to Doxylamine Succinate

Doxylamine Succinate falls under ANTICHOLINERGIC DRUGS — the group Huperzine A interacts with.

Theoretically, huperzine A might decrease the effects of anticholinergic drugs.
Huperzine A has acetylcholinesterase (AChE) inhibiting effects. In animal models, huperzine A reversed cognitive deficits induced by scopolamine, an anticholinergic drug.
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. Doxylamine (the sleep aid in Unisom) works partly by blocking acetylcholine, a brain messenger. Huperzine A pushes in the opposite direction: it raises acetylcholine levels by slowing the enzyme that breaks it down. So in theory, taking the two together could blunt some of doxylamine's effects, meaning it might not make you as drowsy or could leave you tossing and turning.

I want to be honest about how shaky this is, though. This concern comes only from lab and animal research, not real people, so it may not amount to much in practice. It's not dangerous, just possibly less effective. If your nighttime dose isn't doing its job, mention the huperzine A to your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ye JW, Cai JX, Wang LM, Tang XC. Improving effects of huperzine A on spatial working memory in aged monkeys and young adult monkeys with experimental cognitive impairment. J Pharmacol Exp Ther 1999;288:814-9.. DOI
  2. Wang T, Tang XC. Reversal of scopolamine-induced deficits in radial maze performance by (-)-huperzine A: comparison with E2020 and tacrine. Eur J Pharmacol 1998;349:137-42. PubMed
  3. Cheng, D. H., Ren, H., and Tang, X. C. Huperzine A, a novel promising acetylcholinesterase inhibitor. Neuroreport 12-20-1996;8(1):97-101. 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

Huperzine A Also Interacts With Other Medications

Huperzine A has 218 moderate known drug interactions in our database — the Doxylamine Succinate 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. Doxylamine Succinate)
Taking anything else?

Check Another of Your Medications Against Huperzine A

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

From our Q&A

Questions About Huperzine A or Doxylamine Succinate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Huperzine A or Doxylamine Succinate, 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 Doxylamine Succinate

This page covers Huperzine A only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Doxylamine Succinate page lists 52 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Henbane (major), Scopolia (major), Angel's Trumpet (moderate) and Bacopa (moderate).

By severity: 3 major · 38 moderate · 11 minor.

From our pharmacist’s overview on the Doxylamine Succinate page

“Someone reaching for doxylamine succinate (Unisom) to fall asleep is often the same person browsing the supplement aisle, and that pairing deserves genuine care here. Doxylamine is a strongly anticholinergic antihistamine, meaning it dries you out, fogs thinking, and slows digestion, and 30 of the 52 flagged ingredients pile more of th…”

Reviewed by 2 · Jul 18, 2026

Open the Doxylamine Succinate interaction page

One more smart check

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

We hold 86 real supplement products containing Huperzine A, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Huperzine A. Your product may carry other ingredients that interact with Doxylamine Succinate too, on top of Huperzine A — 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 Huperzine A and Doxylamine Succinate 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 Huperzine A
Top half

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

29 days ago today
Medication Doxylamine Succinate
Steady interest

#1,745 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 Huperzine A

What is Huperzine A?

Huperzine A
  • Memory and cognitive support
  • Alzheimer's disease and dementia
  • Age-related memory decline
  • Focus and mental performance
  • Myasthenia gravis (traditional/older use)

Huperzine A is a purified compound from a Chinese clubmoss that acts like a mild cholinesterase inhibitor, similar in mechanism to some prescription Alzheimer's drugs. Some small studies suggest it may modestly help memory in people with dementia, but the evidence is limited and the quality is uncertain. Because it is biologically active and not well standardized, talk with a pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Huperzine A monograph & all interactions
Medication

About Diphenhydramine

What Is Diphenhydramine Used For?

Brand name: Unisom

Diphenhydramine temporarily relieves symptoms of hay fever, other upper respiratory allergies, and the common cold — including runny nose, sneezing, itchy or watery eyes, and itching of the nose or throat.

After Bite Xtra gel is formulated for topical use and is approved to temporarily relieve pain and itching from minor burns, minor cuts and scrapes, insect bites, minor skin irritations, and rashes from poison ivy, poison oak, and poison sumac.

See full Diphenhydramine drug information
Keep checking

Other Drugs & Huperzine A

Browse every other medication we’ve checked against Huperzine A — 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 Huperzine A page.

No interaction 2,611 drugs checked — show the list

We also checked Huperzine A 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 Huperzine A list.

See the full Huperzine A interactions page
See every supplement checked against Doxylamine Succinate, 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
Huperzine A monograph › Uses, safety, and every drug interaction in one place Doxylamine Succinate supplement interactions › Every supplement checked against Doxylamine Succinate, ranked by severity Diphenhydramine 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 Huperzine A and Doxylamine Succinate Together: Common Questions

Can you take Huperzine A with Doxylamine Succinate?
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 Huperzine A and Doxylamine Succinate 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 Doxylamine Succinate and Huperzine A?

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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.