Taken from its natural source, the ephedra plant, ephedrine has been used for medicinal purposes in China for thousands of years. However, the substance is now more often produced by chemical synthesis, marketed in the form of its salt, ephedrine sulfate. The substance, which has a molecular structure similar to amphetamine, works primarily through the release of excitatory chemicals called catecholamines. The catecholamines act on cellular receptors found in numerous body tissues and are responsible for stimulating lipolysis, dilating bronchioles, decreasing appetite, and increasing heart rate and alertness. Ephedrine is sometimes used for its positive effects in medications that treat asthma and congestion.