The term 'appetite suppressant' is used to denote drugs that act primarily on the neurochemical transmitters of the central nervous system to reduce food intake. In addition to drugs that release or mimic the effect of norepinephrine (noradrenaline), this could include drugs that inhibit: reuptake of norepinephrine or 5-hydroxytryptamine (also known as serotonin); bind to the gamma-aminobutyric acid receptors or the cannabinoid receptors; and some peptides that reduce food intake. The sympathomimetic drugs phentermine, diethylpropion, benzphetamine, and phendimetrazine--so named because they mimic many effects of norepinephrine--are only approved in a few countries, and then only for short-term use. Sibutramine, a norepinephrine-5-hydroxytryptamine reuptake inhibitor, is approved for long-term use. Several new mechanisms for drug action are under investigation. Appetite suppressants should be viewed as useful adjuncts to diet and physical activity and might help selected patients to achieve and maintain weight loss.