Club Moss

Huperzine A crosses the blood-brain barrier and inhibits the enzyme acetylcholinesterase, which breaks down acetylcholine in synapses. By preserving acetylcholine longer, huperzine A enhances cholinergic neurotransmission, similar to prescription Alzheimer's drugs (donepezil, rivastigmine) but with a different chemical structure and selectivity profile. Huperzine A also has antioxidant and NMDA receptor-modulating properties that may protect neurons from excitotoxic damage. In China, huperzine A has been studied as a treatment for cognitive decline; some Chinese trials report modest benefit in mild-to-moderate Alzheimer's disease, but Western trials have been smaller and mixed. Note: 'club moss' in older Western herbalism may refer to Lycopodium clavatum, which has different traditional uses and lower huperzine A content.

Huperzine A is typically dosed at 50 to 200 mcg, one to two times daily. Whole-herb Huperzia preparations are dosed by huperzine A content. Cycling (5 days on, 2 days off) is sometimes recommended to limit tolerance, though evidence is limited.

Take huperzine A with food in the morning to minimize nausea and avoid evening dosing that may cause vivid dreams or insomnia. For cognitive support, consistent daily use is more important than precise timing.

Side effects include nausea, vomiting, diarrhea, sweating, vivid dreams, and rare bradycardia. Cholinergic effects can be intense at higher doses.

May potentiate other cholinesterase inhibitors (donepezil, rivastigmine, pyridostigmine), with risk of cholinergic crisis. Anticholinergic drugs (antihistamines, some antidepressants) may reduce huperzine A's effect. Caution with beta-blockers due to potential additive bradycardia.