When used as directed in a comprehensive, physician-supervised weight- loss program that includes a low-fat diet and regular exercise, Tenuate can increase weight loss by about an additional 10%. However, weight loss may not be permanent, especially after this drug is discontinued.

Tenuate limits appetite because of its effects on the hypothalamus, a control center in the brain. The typical dose is 25 mg three times a day an hour before meals with an additional midevening dose if necessary to overcome night hunger, or one 75 mg sustained-release dose a day in midmorning.

Tenuate is chemically related to amphetamine. Years ago, amphetamine was prescribed for weight loss because it is an appetite suppressant. But it often led to drug abuse, so pharmacologists tinkered with its molecular structure to develop similar -- but safer -- compounds. One is diethylpropion, the active ingredient in Tenuate. Others include the active ingredients in the over-the-counter products Acutrim and Dexatrim, and in the prescription medications Mazanor, Sanorex, Fastin, Ionamin, Preludin, Bontril, Plegine, Adipost, Dital, Dyrexan, Melfiat, Prelu-2, Rexigen Forte, and Didrex.

Possible side effects of Tenuate include nervousness, irritability, headache, sweating, dry mouth, nausea, and constipation. Do not take this drug if you are also taking any antidepressant in the chemical family called monoamine oxidase (MAO) inhibitors.