Ephedra is a gymnosperm, one of only three genera in the division Gnetophyta (which is equivalent in taxonomic rank to the whole of the flowering plants). The genus includes about 60 species of shrubby plants with reduced leaves and seeds produced in small cones. They are widely distributed in dry habitats; the species most commonly used medicinally are Eurasian. The listed species are those that may be used interchangeably under the name of Ma Huang according to the Chinese pharmacopoeia. There are a dozen North American species; E. nevadensis in particular has often been used to make a traditional beverage known as Mormon tea.

The bioactivity of ephedra is due largely to its content of ephedrine alkaloids. These alkaloids are present in active quantities in a number of Eurasian species, but in no North American species so far as is known. Traditional preparations of ephedra are used for asthma, and pharmaceutical drugs derived from ephedrine and having similar physiological effects (e.g., pseudoephedrine) are similarly used for asthma and congestion. Until recently, ephedra was combined with caffeine or caffeine-containing plants in a number of dietary supplements marketed for weight loss.

Ephedrine is a stimulant that may cause vasoconstriction and slightly elevated blood pressure. This means that it poses several safety issues, including unpleasant side effects, interactions with certain pharmaceuticals, and potential risks to consumers with medical conditions such as hypertension or glaucoma. Finished dietary supplements containing ephedra have therefore been removed from the market as excessively hazardous, although products defined as traditional foods (tea blends) remain legal. Some herbalists argue that many of the Western reports of illness associated with ephedra consumption are attributable to inappropriate use of high-dose concentrated products, which would not have been used in traditional Chinese herbal practice.

Selected References

Boozer, C. N., P. A. Daly, P. Homel, et al. 2002. Herbal ephedra/caffeine for weight loss: a 6-month randomized safety and efficacy trial. Int. J. Obes. Relat. Metab. Disord. 26: 593-604.

Fu L., Yu Y., and H. Riedl. 1999. Ephedraceae. Pp. 97-101 in Wu Z. and P. H. Raven (eds.), Flora of China vol. 4. Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, MO.

Graham, R. J. D. 1908. On the histology of the Ephedreae, with special reference to the value of histology for systematic purposes. Trans. Roy. Soc. Edinburgh 46: 203-212.

Haller, C. A., and N. L. Benowitz. 2000. Adverse cardiovascular and central nervous system events associated with dietary supplements containing ephedra alkaloids. N. Engl. J. Med. 343: 1833-1838.

Kalman, D., T. Incledon, I. Gaunaurd, H. Schwartz, and D. Krieger. 2002. An acute clinical trial evaluating the cardiovascular effects of an herbal ephedra-caffeine weight loss product in healthy overweight adults. Int. J. Obes. Relat. Metab. Disord. 26: 1363-1366.

Pharmacopoeia Commission of PRC, eds. 1997. Pharmacopoeia of the People?s Republic of China, English ed., vol. 1. Chemical Industry Press, Beijing.

Shekelle, P. G., M. L. Hardy, S. C. Morton, et al. 2003. Efficacy and safety of ephedra and ephedrine for weight loss and athletic performance: a meta-analysis. JAMA 289:1537-1545.

Stevenson, D. W. 1993. Ephedraceae. Pp. 428-434 in Flora of North America Editoral Committee (eds.), Flora of North America vol. 2. Oxford University Press, New York.