Huperzine A (pronounced HOOP-ur-zeen) is a moss extract that has been used in traditional Chinese medicine for centuries. It has properties similar to those of cholinesterase inhibitors, one class of FDA-approved Alzheimer medications. As a result, it is promoted as a treatment for Alzheimer's disease.
What is Huperzine?
Huperzine, an anticholinesterase alkaloid, is divided into two chemical species, huperzine A and huperzine B, which have similar effects but differing activity levels (huperzine A being about 10 times as strong as huperzine B). Huperzine A was first isolated from the Chinese herb Lycopodium serratum in 1980 at the Zhejiang Academy of Medical Sciences and the Shanghai Institute of Materia Medica of the Chinese Academy of Sciences. Huperzine B was isolated five years later. The plant source, originally called Qian Ceng Ta, meaning thousand-layers pagoda (referring to the tall multi-leafed appearance of the plant), is also known in China as Jin Bu Huan, a term meaning "more valuable than gold," usually applied to plants that have potent analgesic actions.
A number of animal studies have documented that huperzine A is a long acting acetylcholinesterase inhibitor with greater potency than tacrine or donepezil, two cholinesterase inhibitors approved for the treatment of Alzheimer's disease (AD). Huperzine A also appears to decrease neuronal cell death in the brain. Well designed human trials with huperzine A have not been published in the Western medical literature. Four clinical trials have been published in China, where it has been approved for treating dementia for many years. One of these studies was an 8 week, double-blind, placebo controlled trial of 103 patients with AD. Among patients who took 200 mcg of huperzine A twice daily, 58% improved in memory, cognition, behavior and function, compared to 36% of patients who took placebo. A derivative of huperzine A, huprine X, is also currently of interest for the treatment of AD.
Recently, the Alzheimer's Disease Cooperative Study (ADCS) conducted the first large-scale U.S. clinical trial of huperzine A as a treatment for mild to moderate Alzheimer’s disease. And the results were not so encouraging so far. Participants taking huperzine A experienced no greater benefit than those taking a placebo.
Huperzine A has been evaluated at the Mayo Clinic in Jacksonville, Florida. According to Alan Kozikowski, a chemist who is heading the research there, Huperzine A is more effective and more specific than tacrine, another anticholinesterase drug. Interneuron Pharmaceuticals in Lexington, Mass. is testing Huperzine A in human clinical trials.
Side Effects and Safety
No serious side effects have been reported with huperzine A. As a result of greater selectivity for central acetylcholinesterase, huperzine A may cause fewer cholinergic side effects (e.g., nausea, vomiting, diarrhea, anorexia) than tacrine, donepezil or rivastigmine. Bradycardia was reported in one clinical trial. Individuals with heart conditions should not use huperzine A without guidance from a physician. Possible contraindications include sick sinus syndrome and bradycardia. As an acetylcholinesterase inhibitor, huperzine A can be expected to interact with cholinergic agonists, anticholinergic drugs, and the muscle relaxant, succinylcholine.
Huperzine A should be avoided by children, pregnant women and nursing mothers. Because of possible adverse effects in those with seizure disorders, cardiac arrhythmias and asthma, those with these disorders should avoid huperzine A. Those with irritable bowel disease, inflammatory bowel disease and malabsorption syndromes should avoid huperzine A.
There are various forms of huperzine A available, including extracts of Huperzia serrata, natural (-)-huperzine A and synthetic racemic (±)-huperzine A. Natural (-)-huperzine A is approximately three times more potent than the synthetic racemic mixture. The doses of natural (-)-huperzine A used in clinical studies ranged from 60 micrograms to 200 micrograms daily. Huperzine A should only be used with a physician's recommendation and monitoring. Now, it is mostly supplied in Capsules — 50 mcg and in Tablets — 50 mcg.
Because currently available formulations of huperzine A are dietary supplements, they are unregulated and manufactured with no uniform standards. Taking these unregulated preparations could increase the risks of serious side effects, especially if used in combination with FDA-approved Alzheimer drugs. It also can be a broad range of substances of differing quality.
For now, most doctors don't recommend taking huperzine A because FDA-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 cause stronger side effects, such as nausea, vomiting, diarrhea, dizziness and muscle cramps. Consult with your doctor before starting any dietary supplement, including huperzine A.
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