Huperzine A

Inhibits the breakdown of the neurotransmitter acetylcholine (ACh) by the enzyme acetylcholinesterase.
Antagonist of the NMDA-receptor.
Reversible acetylcholinesterase inhibitor
Mild cholinergic side effects such as nausea, vomiting, and diarrhea.
Toxicology studies show huperzine A to be non-toxic even when administered at 50-100 times the human therapeutic dose.
The extract is active for 6 hours at a dose of 2 μg/kg with no remarkable side effects.
Huperzine A might be useful in the treatment of organophosphate nerve agent poisoning by preventing damage to the central nervous system caused by such agents.