The ephedra species are tall plants that grow in arid regions of the World. Chinese ephedra (Ephedra sinica) is also called Ma Huang and is the species found in Asia, whereas European ephedra (Ephedra distachya) is the form found in Europe. Other species include Phedra viridis, Ephedra gerardiana, Ephedra nevadensis and Ephedra americana. Ephedra plants contain alkaloids which are believed to be the active ingredients in preparations. The total alkaloid content of ephedra is around 3 to 4 % with 50 to 90 percent of this being the alkaloid ephedrine and the remaining alkaloids comprising pseudoephedrine and norpseudoephedrine. The alkaloid content of other ephedrine species varies with Ephedra nevadensis containing no ephedrine. Ephedra has been used in Chinese medicine for millennia to treat asthma, hay fever, bronchitis arthritis and hypotension. Ephedrine and pseudoephedrine were chemically synthesised in the 1920’s and since then have been used as cold and flu remedies.
Ephedrine and pseudoephedrine are beta adrenergic agonist and in this regard are able to mimic the effects of adrenaline. This puts ephedrine in the same group of drugs as amphetamine, although the effects of ephedrine are much milder than in the case of amphetamine. Ephedrine therefore has a pronounced effect on the cardiovascular system, and in particular is able to increase heart rate and the force of contraction of heart muscle. This explains the ability of ephedrine to treat hypotension. Ephedrine and pseudoephedrine can relax bronchial muscle because there are beta adrenergic receptors in the airway. This is a similar mechanism by which clenbuterol and salbutamol are able to relax the airway. This explains the ability of ephedrine to treat rhinitis, hay fever and asthma. Pseudoephedrine tends to be a better bronchial drug than ephedrine because it has fewer of the cardiovascular and central nervous system side effects. Ephedrine also stimulates the central nervous system giving users a strong motivational desire.
Perhaps the most famous use for ephedra is as a weight loss aid. Clinical studies attest the the effectiveness of ephedra preparations in this regard. Based on its performance in clinical trials it could be argued that there is no better weight loss drug. The ability of ephedra to cause weight loss likely relates to the presence of the ephedrine it contains. Ephedrine is able to stimulate beta adrenergic receptors on fat cells and this causes a breakdown of triglycerides to fatty acids. At the same time, ephedrine stimulates substrate utilisation and the fatty acids are oxidised to produce heat. Estimates from studies show that ephedrine may increase heat production by 40 %, with most of the energy for this being derived from fat. Ephedrine is also an effective weight loss drug because it causes a retention of skeletal muscle that allows the resting metabolic rate to be maintained at a higher level than would normally be possible during weight loss. This is a shame, because ephedra is no longer available for sale in the United Kingdom, despite an excellent safety record..
The thermogenic effects of ephedrine are enhanced by concomitant administration of methylxanthines (e.g. caffeine) and salicylates (e.g. aspirin). Studies involving just isolated ephedrine have shown weight loss effects, but the results from such studies are inconsistent. This likely relates to the fact that the addition of methylxanthines and salicylates is required to get the most thermogenic benefit from ephedrine. Most studies using a combination of ephedrine and caffeine have used roughly ten times the dose of caffeine to ephedrine. For example, if 20 mg of ephedrine was administered the dose of caffeine required for effective synergism is roughly 200 mg. A similar formula is used to optimise the intake of aspirin for a synergistic effect. Therefore 20 mg of ephedrine would be taken with 200 mg of caffeine and 200 mg of aspirin. This regimen is usually repeated 3 times per day, with the last dose being around late afternoon, so that sleep is not disturbed by the pronounced stimulating effect of the ephedrine and caffeine.