Huperzine A

Tier 3 — weak evidence · Cognition · Acetylcholinesterase

Isolated from Chinese club moss, inhibits acetylcholinesterase, raising brain acetylcholine levels. Small Chinese RCTs reported memory and cognitive improvements in Alzheimer patients. Long half-life — can accumulate with daily use. Side effects include nausea, diarrhoea, and bradycardia. Never combine with prescription cholinesterase inhibitors (donepezil, rivastigmine).

Dose: 50–200 mcg twice daily; do not combine with prescription cholinesterase inhibitors