Huperzine (HOOP-ur-zeen) A, a dietary supplement derived from the Chinese club moss Huperzia serrata, has received some interest as a potential treatment for Alzheimer's disease.

Huperzine A acts as a cholinesterase inhibitor — a type of medication that works by improving the levels of neurotransmitters in the brain. Small early studies suggest that huperzine A may improve memory and protect nerve cells, which could slow the cognitive decline associated with Alzheimer's.

A recent meta-analysis found evidence that huperzine A may significantly improve cognitive performance in patients with Alzheimer's disease. Another study suggests that huperzine A appears to have many protective effects on the brain in addition to its role as a cholinesterase inhibitor.

However, there is a lack of long-term safety data — most studies have lasted three months or less — and many participants in the trials experienced side effects, including nausea and vomiting. More studies are needed to determine possible benefits and long-term risks of huperzine A.

For now, most doctors don't recommend taking huperzine A because Food and Drug Administration-approved cholinesterase inhibitor medications are available that have been tested for safety and effectiveness.

The Alzheimer's Association recommends that you not take huperzine A if you're already taking a prescribed cholinesterase inhibitor, such as donepezil (Aricept), rivastigmine (Exelon) or galantamine (Razadyne). Taking both could increase your risk of serious side effects.

Consult with your doctor before starting any dietary supplement, including huperzine A.

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Nov. 25, 2014 See more Expert Answers