Drug treatment of obesity

At present only two drugs are approved for long-term treatment of obesity. Sibutramine inhibits the reuptake of serotonin and norepinephrine. In clinical trials it produces a dose-dependent 5-10% decrease in body weight. Its side effects include dry mouth, insomnia, asthenia, and constipation. In addition, sibutramine produces a small increase in blood pressure and pulse that is a contraindication to the use of this drug in some individuals with heart disease. Xenical is the other drug approved for long-term use in the treatment of obesity. It works by blocking lipase and thus increasing the fecal loss of triglyceride. One valuable consequence of this mechanism of action is the reduction of serum cholesterol that averages about 5% more than can be accounted for by weight loss alone. In clinical trials it produces a 5-10% loss of weight. Its side effects are entirely due to undigested fat in the intestine that can lead to increased frequency and change in the character of stools. It can also lower fat-soluble vitamins. The ingestion of a vitamin supplement before bedtime is a reasonable treatment strategy. The effect on weight loss during long-term trials with these two drugs is shown in Figs 7 and 8 above. Also in this figure is data on phentermine used in trials of six months or more. Although there were differences in mean weight losses with these drugs, when the placebo effect was taken into account they all had a surprisingly similar magnitude of weight loss.