Huperzine A
A plant alkaloid and potent, reversible acetylcholinesterase inhibitor studied for Alzheimer's disease, mainly in China. It has real cholinergic pharmacology and moderate human data, but its potency means cholinergic side effects and interaction risks are genuine.
01 Overview
Huperzine A is an alkaloid isolated from the club moss Huperzia serrata, used in traditional Chinese medicine. It is a selective, reversible acetylcholinesterase inhibitor that crosses the blood-brain barrier, and has been studied in China for Alzheimer's disease and vascular dementia with some positive but methodologically limited trials.
It is sold as a supplement in the US and used as a nootropic. Because it genuinely inhibits acetylcholinesterase, it can interact with other cholinergic drugs and produce classic cholinergic side effects at higher doses.
02 Mechanism
Selectively and reversibly inhibits acetylcholinesterase, raising synaptic acetylcholine; also reported to have NMDA-receptor antagonism and neuroprotective effects.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Common | 50–200 mcg/day | Oral | Micrograms, not milligrams; potent AChE inhibitor. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Cognitive improvement in dementiaChinese trials reported cognitive benefit in Alzheimer's; quality is limited. | Modest | Clinical | |
| Raised acetylcholine / memory supportConsistent with its AChE-inhibiting pharmacology. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Cholinergic side effectsNausea, sweating, hypersalivation, diarrhoea, and slowed heart rate at higher doses. | Moderate | Dose-dependent | Clinical | |
| Bradycardia / cardiovascular effectsSlowed heart rate can occur with cholinergic excess. | Moderate | Rare | Clinical |