Huperzine A

Scientific Name(s):Isolated from Huperzia serrata (Thunb.) Trev. (synonym Lycopodium serratum Thunb) Family: Lycopodiaceae (club moss)

Common Name(s): Club moss , Chien Tseng Ta , Jin Bu Buan , Qian Ceng Ta , She Zu Cao , Shi Song . Other products containing huperzine A include Memorzine , Brainmax , Neuroflow .

Uses

Historically, club moss has been used for the treatment of bruises, strains, swelling, rheumatism, and colds, to relax muscles and tendons, and to improve blood circulation. Because of its anticholinesterase activity, huperzine A, a constituent of the whole plant, has been studied for potential use in treating Alzheimer disease and other CNS disorders; however, there is still insufficient evidence to support its routine use.

Dosing

Huperzine A has been studied at oral dosages of 0.2 to 0.4 mg/day for Alzheimer disease.

Contraindications

Contraindications have not been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

In clinical trials, cholinergic adverse reactions have been noted, including hyperactivity, nasal obstruction, nausea, vomiting, diarrhea, insomnia, anxiety, dizziness, thirst, and constipation. One trial reported abnormalities in electrocardiogram (ECG) patterns (cardiac ischemia and arrhythmia).

Toxicology

Symptoms of acute toxicity are similar to those of other cholinergic inhibitors and include muscular tremor, drooling, tears, increased bronchial secretions, and incontinence. No mutagenicity or teratogenicity were found in rodent studies.

Botany

Huperzine A is isolated from the club moss Huperzia serrata , also known as Lycopodium serratum Thunb. Distributed worldwide, club moss is found in subtropical zones of the United States and in southern China. It has been extensively cultivated and may be threatened in the wild in China.

Club mosses are primitive, vascular plants that differ from true mosses by having specialized fluid-conducting tissues, but, like mosses, they reproduce by means of spores, which are either clustered into small cones or born in the axils of the small, scale-like leaves. Plants older than 15 years may only grow to 10 cm in height. Some species of Lycopodium are called ground pine or creeping cedar, especially those that resemble miniature hemlocks, with flattened fan-shaped branches often used for Christmas decorations. 1 , 2

History

The use of club moss can be traced back to the Chinese pharmacopoeias of the Tang dynasty as Shi Song, used for the treatment of rheumatism and colds, to relax muscles and tendons, and to improve blood circulation. As Qian Ceng Ta, it has been used for the treatment of bruises, strains, and swelling, and, more recently, for organophosphate poisoning, myasthenia gravis, and schizophrenia. The study of the chemistry and pharmacology of the plant and its alkaloids gained momentum in the 1980s from Chinese scientists. 3 , 4 , 5 , 6

Chemistry

A review of the chemical composition of club moss has been published. The plant contains mainly alkaloids, triterpenes, flavones, and phenolic acids. Four major structural classes of Lycopodium alkaloids have been described, including lycopodine, lycodine (to which huperzine A belongs), fawcettimines, and others. 4 The yield of huperzine A from H. serrata is reported to be approximately 0.1% on a dry weight basis. 7

Huperzine analogs have been synthesized to improve binding and pharmacological actions. More detailed analyses of huperzine B and the enantiomer of natural huperzine A have also been made. 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16

Uses and Pharmacology

Huperzine A is approved for use as a drug for the treatment of Alzheimer disease in China; however, it is regulated as an herbal supplement in the United States. 17 Several firms (Solgar, Pharmavite, GNC, Kingchem, and NOW Foods) filed the required premarket notifications with the Food and Drug Administration between 1997 and 2000 for huperzine A products manufactured in China from natural sources. 18

Alzheimer disease

A Cochrane review of the effect of huperzine A in Alzheimer disease has been published, as well as other reviews. 19 , 20 , 21 All reviews note the lack of quality long-term clinical trials to support definitive statements about a place in therapy for huperzine A, despite the numerous clinical studies being undertaken. 19 , 20 , 22

Animal data

Animal and in vitro experiments have been conducted, and the mechanism of action for huperzine appears to be a combination of anticholinesterase activity and antiglutamate, antioxidant, and neuroprotective effects. 6 , 9 , 19 , 21 , 22 , 23 , 24 , 25 , 26 Huperzine A crosses the blood-brain barrier more effectively than tacrine or donepezil and acts with greater potency than tacrine, physostigmine, or galanthamine. 22 , 27 Huperzine A is selective for brain acetyl cholinesterase over plasma butyryl cholinesterase, which may account for its reported lower adverse effect profile in clinical studies. 22 , 28

Clinical data

Based on limited data, some beneficial effects are attributed to huperzine A in Alzheimer disease, including an increase in general cognitive function, global clinical status, behavioral disturbances, and physical performance. Not all measurement scales found positive effects for huperzine A over placebo. 19 The results of a US multicenter, phase 2 clinical trial (now closed), in which huperzine A was evaluated at 2 different doses versus placebo, are awaited. 22 , 29

Other CNS effects
Dementia

High quality clinical trials are lacking; however, 1 review of 4 clinical trials found improvement against memory, dementia, and Alzheimer scales, 30 while a Cochrane review found only 1 clinical trial meeting inclusion criteria in which no difference compared with placebo was found for vascular dementia. 31

Epilepsy

Anticonvulsant activity of huperzine A has been demonstrated in mice, and a pilot clinical study is being undertaken. 32

Organophosphate antidote

Huperzine A's potent inhibition of cholinesterase has also made it a candidate for prevention of poisoning by the nerve agent soman and other organophosphates. In contrast to pyridostigmine, huperzine A crosses the blood-brain barrier and, therefore, may be effective in preventing seizures and other neuropathology caused by soman. 6 , 33 Animal experiments have demonstrated activity against soman-induced seizures and mortality; however, clinical studies are lacking. 9 , 33 , 34 , 35 , 36 , 37

Parkinson disease

Protective effects have been demonstrated in mice models, but clinical trials are lacking. 38

Schizophrenia

A small (N = 19), open-label clinical study found improved cognitive effects for huperzine A over 12 weeks. 39 Clinical trials on the use of huperzine in schizophrenia in the United States are being prepared for recruitment. 40 , 41

Dosage

Huperzine A in pure form has been studied at oral dosages of 0.2 to 0.4 mg/day for Alzheimer disease. It has also been administered intramuscularly at 0.06 to 0.4 mg/day in dementia studies. 9 , 19 , 20 , 21 , 22 , 30

In an open-label study among patients with schizophrenia, 0.3 mg/day for 12 weeks was used. 39

The pharmacokinetics of huperzine A have been studied in healthy adult volunteers. A half-life of 288 minutes was reported, comparable with that of donepezil, while no tolerance was noted with multiple dosing. 22 Transdermal patches have been tested in beagles. 6

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

Concomitant use of huperzine A with cholinesterase inhibitors could lead to potentiation of adverse reactions, although case reports are lacking. 21

In vitro studies suggest potentiation of huperzine A by the green tea polyphenol epigallocatechin-3-gallate. 42

Adverse Reactions

In clinical trials, cholinergic side effects were noted, including hyperactivity, nasal obstruction, nausea, vomiting, diarrhea, insomnia, anxiety, dizziness, thirst, and constipation. One trial reported abnormalities in ECG patterns (cardiac ischemia and arrhythmia). 19

Toxicology

Symptoms of acute toxicity are similar to those of other cholinergic inhibitors and include muscular tremor, drooling, tears, increased bronchial secretions, and incontinence. 22

The acute oral median lethal dose of huperzine A in rats has been reported as 4.6 mg/kg and as an intravenous dose of 0.63 mg. 4 One toxicological study reported increases in serum aminotransferases. 6 No pathological changes were found in histological studies of the liver, kidney, heart, lungs, or brain after 180 days of administration, and no mutagenicity or teratogenicity were found in rodent studies. 4

Bibliography

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