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To clarify the efficacy of antiobesity drugs, this article reviews all long-term (> or =36 weeks), placebo-controlled trials of obesity pharmacotherapy published since 1960. Since fears of anorexiant-induced heart valve damage preclude many physicians and patients from even considering antiobesity drugs, this area is also reviewed in-depth. Electronic database and manual bibliography search was used to identify all relevant publications. While existing studies are too few and heterogeneous to warrant meta-analysis, their review does provide evidence highly relevant to the safety and efficacy of available anorexiants. Weight loss attributable to obesity pharmacotherapy (ie, in excess of placebo) in trials lasting 36 to 52 weeks was 8.1% or 7.9 kg for those receiving phentermine resin, 5.0 % or 4.3 kg for those receiving sibutramine hydrochloride, 3.4% or 3.4 kg for those receiving orlistat, and -1.5% or -1.5 kg for those receiving diethylpropion hydrochloride. Physiologic, pathologic, and epidemiological studies strongly support that anorexiant-induced valvulopathy is attributable to specific serotonergic properties of the fenfluramines that are not present with available weight loss drugs.

We performed a double-blind, controlled clinical trial comparing phentermine resin (30 mg in the morning), fenfluramine hydrochloride (20 mg three times a day), and a combination of phentermine resin (15 mg in the morning) and fenfluramine hydrochloride (30 mg before the evening meal), and placebo. We combined low doses of the two drugs to maintain efficacy while diminishing adverse effects. Eighty-one people with simple obesity (130% to 180% of ideal body weight) participated. Individualized diets were prescribed and discussed again during the 24-week study period. Weight loss in those receiving the combination (8.4 +/- 1.1 kg; mean +/- SEM) was significantly greater than in those receiving placebo (4.4 +/- 0.9 kg; Scheff é's test) and equivalent to that of those receiving fenfluramine (7.5 +/- 1.2 kg) or phentermine (10.0 +/- 1.2 kg) alone. Adverse effects were less frequent with the combination regimen than with other active treatments. Thirty-seven participants dropped out of the study, 18 for reasons related to drug treatment. Combining fenfluramine and phentermine capitalized on their pharmacodynamic differences, resulting in equivalent weight loss, fewer adverse effects, and better appetite control.