d. klein/getty images

Lorcaserin

Currently in clinical trials, this drug works by activating a serotonin receptor in the brain that helps regulate appetite and metabolism. Early tests demonstrated that lorcaserin produced significant and progressive weight loss over a twelve-week period and was generally well tolerated at all doses. The drug, which hasn’t shown safety issues so far, has been under intense scrutiny by analysts who are concerned about its marketing viability, since lorcaserin is said to work similarly to now discontinued fen-phen, which caused heart problems. However, Arena Pharmaceuticals, the company that makes the drug, says lorcaserin is much more selective in the receptors it affects. In clinical trials, the drug had no apparent effects on heart valves or pulmonary artery pressure.

d. grill/getty images

Off-Label Weight-Loss Drugs

Many doctors believe it is sometimes appropriate to prescribe drugs for indications that have not been approved by the FDA—a practice known as off- label use. Off-label use is legal and, with important qualifications, generally embraced by physicians and other health- care providers, health-care institutions, insurers, pharmaceutical companies, and even the FDA. Before prescribing a drug for a use not on the approved label, doctors must be very well informed about the drug, its side effects, and the condition of their patients. Off-label use is not to be undertaken lightly or casually but with wisdom, firm scientific rationale, and sound medical evidence.