Ephedrine is similar in structure to the derivatives amphetamine and methamphetamine. Structurally, ephedrine is a substituted amphetamine and methamphetamine analogue, ephedrine differs from methamphetamine only by the presence of a hydroxyl (OH) group at the Rß position. Chemically, it is an alkaloid derived from various plants in the genus Ephedra. Ephedrine stimulates lipolysis by increasing noradrenaline (NA) release from sympathetic nerve terminals. This increase in noradrenaline activates adrenergic receptors which increases cAMP levels in fat cells and muscle cells. This has the effect of increasing lipolysis in fat cells and increasing protein synthesis in muscle tissue. Negative feedback mechanisms are activated as well, and involve the production of phosphodiesterases, adenosine, and prostaglandins.