Huperzine A is an alkaloid from club moss (Huperzia serrata). It blocks acetylcholinesterase, the enzyme that dismantles acetylcholine. That neurotransmitter drives learning and memory.
People use it to sharpen mental clarity, focus, and recall, especially older adults or anyone chasing cognitive support. Mood and alertness effects show up in some studies, though the evidence is thinner there.
Standard doses land between 50 and 200 micrograms, once or twice daily. Taking it with food can reduce stomach upset. Many feel the effect within 30 to 60 minutes, and it typically lasts several hours.
Side effects may include dizziness, blurred vision, nausea, or a slow heart rate. Avoid pairing it with Alzheimer's drugs like donepezil or rivastigmine, or other cholinergic agents. Anyone with a heart condition, asthma, or epilepsy needs to be cautious. Do not take it during pregnancy or breastfeeding.