SupplementPreliminary evidenceImmunity

Huperzine A

Chinese club moss alkaloid that is a reversible acetylcholinesterase inhibitor, preliminary RCT signal in mild cognitive impairment.

Why

Huperzine A is an alkaloid isolated from the Chinese club moss (Huperzia serrata), used historically in Chinese medicine and now produced as a standardised supplement. Pharmacologically it is a reversible acetylcholinesterase inhibitor, the same mechanism as donepezil and rivastigmine, but at much smaller mg-doses. Small Chinese RCTs report cognitive improvement in mild cognitive impairment and Alzheimer's; Cochrane review in 2008 noted methodological limitations but a directional signal. In China, huperzine A is registered as a prescription medication.

How it works

Reversible, selective inhibitor of acetylcholinesterase, increases synaptic acetylcholine. NMDA-receptor antagonism may provide additional neuroprotective effect. Long elimination half-life (~12 hours) supports once-daily dosing.

Expected onset · Cognitive effects assessed over 8–12 weeks in trial protocols

How to take

Dosage

100–400 µg/day divided. Higher doses used in Chinese clinical trials.

Timing

Divided morning and afternoon

On the label

Stated huperzine A content in micrograms (not milligrams). Third-party tested for purity. Synthetic huperzine A is more consistent than crude Huperzia serrata extract.

Ideal for

Adults with mild cognitive impairment exploring cholinergic-pathway support, under clinical supervision given the AChE-inhibitor pharmacology.

Safety

Carries the cholinergic side-effect profile of pharmaceutical AChE inhibitors: nausea, vomiting, diarrhoea, bradycardia, hypotension, increased salivation, urinary urgency. Not for combination with donepezil or rivastigmine (additive AChE inhibition). Avoid in cardiac conduction disorders, asthma, peptic ulcer, urinary obstruction, epilepsy. Avoid in pregnancy and breastfeeding. Treat as a medication, not a casual supplement.

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Evidence

At a glance

Cochrane 2008 SR on huperzine A for Alzheimer's: 6 Chinese RCTs reported cognitive improvement vs placebo at 8–24 weeks, with methodological concerns limiting strength of conclusion. Registered as a prescription medication in China, clinical-grade regulatory standing there, but not yet in Western markets. Preliminary evidence, no Cochrane review, EMA HMPC monograph or EFSA-authorised health claim covers this indication; cited RCTs are small or in non-tier-1 journals. Useful as honest reference rather than evidence-grade recommendation.

Limitations

Methodological concerns in the existing trial base limited the Cochrane review's confidence in effect size. No Western regulatory approval; pharmacology is real and merits the medication-style precautions captured in the caution field.

Where to get it

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