Orlistat or tetrahydrolipstatin (Xenical, Hoffmann-La Roche) is a saturated derivative of lipstatin originally isolated from Streptomyces toxytricini. Orlistat (Xenical, Hoffmann-La Roche) is a powerful inhibitor of gastrointestinal lipase and as such, reduces fat absorption. Orlistat acts by binding covalently to the serine residue of the active site of gastric and pancreatic lipases. When administered with fat-containing foods, orlistat partially inhibits hydrolysis of triglycerides, thus reducing the subsequent absorption of monoaclglycerides and free fatty acids. Unlike other weight-reducing drugs it is minimally absorbed and has no effects in the CNS. Xenical is indicated for obesity management including weight loss and weight maintenance when used in conjunction witha reduced-calorie diet. XENICAL is also indicated to reduce the risk for weight regain after prior weight loss. XENICAL is indicated for obese patients with an initial body mass index (BMI) ≥ 30 kg/m2 or ≥ 27 kg/m2 in the presence of other risk factors (eg, hypertension, diabetes, dyslipidemia). In addition to its well established efficacy in achieving modest weight loss, orlistat has been shown to improve glycaemic parameters in obese adults with type 2 diabetes mellitus as well as some features of the metabolic syndrome.

Benzphetamine is a sympathomimetic agent with properties similar to dextroamphetamine. It is used in the management of exogenous obesity as a short term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction in patients with an initial body mass index (BMI) of 30 kg/m2 or higher who have not responded to appropriate weight reducing regimen (diet and/or exercise) alone. Presumably, benzphetamine produces its effects through mechanisms similar to amphetamine via induces synaptic vesicular amine transporter, but precise mechanism of action of benzphetamine is not known.

Phentermine is an amphetamine that stimulates neurons to release or maintain high levels of a particular group of neurotransmitters known as catecholamines; these include dopamine and norepinephrine. High levels of these catecholamines tend to suppress hunger signals and appetite. The drug seems to inhibit reuptake of noradrenaline, dopamine, and seratonin through inhibition or reversal of the reuptake transporters. It may also inhibit MAO enzymes leaving more neurotransmitter available at the synapse. Phentermine (through catecholamine elevation) may also indirectly affect leptin levels in the brain. It is theorized that phentermine can raise levels of leptin which signal satiety. It is also theorized that increased levels of the catecholamines are partially responsible for halting another chemical messenger known as neuropeptide Y. This peptide initiates eating, decreases energy expenditure, and increases fat storage. Phentermine is indicated in the management of exogenous obesity as a short term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction. Phentermine hydrochloride is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, the amphetamines. Actions include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

Lorcaserin, currently marketed under the trade name Belviq and previously Lorqess during development, is a weight-loss drug developed by Arena Pharmaceuticals. Lorcaserin is a selective 5-HT2C receptor agonist, and in vitro testing of the drug showed reasonable selectivity for 5-HT2C over other related targets. 5-HT2C receptors are located almost exclusively in the brain, and can be found in the choroid plexus, cortex, hippocampus, cerebellum, amygdala, thalamus, and hypothalamus. The activation of 5-HT2C receptors in the hypothalamus is supposed to activate proopiomelanocortin (POMC) production and consequently promote weight loss through satiety. This hypothesis is supported by clinical trials and other studies. While it is generally thought that 5-HT2C receptors help to regulate appetite as well as mood, and endocrine secretion, the exact mechanism of appetite regulation is not yet known. Lorcaserin has shown 100x selectivity for 5-HT2C versus the closely related 5-HT2B receptor, and 17x selectivity over the 5-HT2A receptor

Phendimetrazine is an appetite suppressant that is FDA approved for the treatment of exogenous obesity. It is clinically available anorectic agent, which display minimal interactions with monoamine transporters in vitro. On the other hand, their medications is known to be psychomotor stimulants when administered in vivo as indicated by their shared properties with illicit drugs like cocaine. The following adverse reactions are described, or described in greater detail, in other sections: Primary pulmonary hypertension; Valvular heart disease; Effect on the ability to engage in potentially hazardous tasks; Withdrawal effects following prolonged high dosage administration. Use of phendimetrazine tartrate is contraindicated during or within 14 days following the administration of monoamine oxidase inhibitors because of the risk of hypertensive crisis.

Diethylpropion is a sympathomimetic stimulant drug marketed as an appetite suppressant. Chemically, it is the N,N-diethyl analog of cathinone. Its mechanism of action is similar to other appetite suppressants such as sibutramine, phentermine and dextroamphetamine. Diethylpropion is an amphetamine that stimulates neurons to release or maintain high levels of a particular group of neurotransmitters known as catecholamines; these include dopamine and norepinephrine. High levels of these catecholamines tend to suppress hunger signals and appetite. Diethylpropion (through catecholamine elevation) may also indirectly affect leptin levels in the brain. It is theorized that diethylpropion can raise levels of leptin which signal satiety. It is also theorized that increased levels of the catecholamines are partially responsible for halting another chemical messenger known as neuropeptide Y. This peptide initiates eating, decreases energy expenditure, and increases fat storage. It is used in the management of exogenous obesity as a short-term adjunct (a few weeks) in a regimen of weight reduction based on caloric restriction.

Subitramine is a potent inhibitor of monoamines (serotonin, dopamine, noradrenaline) reuptake that was approved by FDA for the treatmen of obesity. Sibutramine is metabolized to metabolites M1 and M2 which are more active toward the monoamine transporters.The drug was withdrawn from the market because of clinical trial data indicating an increased risk of heart attack and stroke. It was sold under a variety of brand names including Reductil, Meridia and Sibutrex.