The Role of Weight Loss Drugs in Fighting Obesity

Orlistat

• Orlistat (Xenical) is a malabsorption enhancer and works by reducing the net dietary fat absorption by about 30%. This results in a reduced absorption of approximately 200-300 calories per day.
• It may cause unpleasant gastrointestinal side effects.
• A low-fat diet minimizes side effects. Patients should be informed that excessive fat ingestion may lead to uncomfortable symptoms of gas, cramping, and oily stools.
• It reduces absorption of certain vitamins; taking a daily multivitamin is recommended.
• There are no recognized contraindications for orlistat.
• The two main orlistat trials, both of which lasted two years, resulted in a weight loss of about 9%-10% during the first year compared with 4%-6% for placebo-treated subjects.

Sibutramine

• A medication approved for appetite suppression or satiety enhancement class is sibutramine (Meridia).
• Sibutramine works by increasing the activity of certain chemicals in the brain: serotonin and norepinephrine, which results in a feeling of satiety.
• It's most effective when used in combination with a reduced calorie diet.
• The safety and efficacy of sibutramine have been demonstrated in clinical trials. Weight loss in these trials averaged 5%-10% with maintenance of weight loss for up to 18 months.
• Sibutramine may cause cardiovascular side effects, such as a small increase in blood pressure and heart rate.
• Drug interactions and contraindications should be considered when prescribing appetite suppressants.

Phentermine

• Phentermine works by suppressing appetite.
• It's most effective when used in combination with diet and exercise.
• Common side effects (eg, dry mouth, ]]>insomnia]]> ) tend to be minor and short-lived.
• Potential side effects include cardiovascular risks.
• Phentermine was part of the “fen-phen” combination that led to dangerous circulatory complications (the other part, fenfluramine, was removed from the market in 1997 due to safety concerns).

What the Research Says

Research has focused on the effectiveness of orlistat and sibutramine. Here is a look at some research on these drugs:

• A study in the Cochrane Review compared the effectiveness and safety of approved anti-obesity medications in clinical trials of at least one-year duration. The researchers looked at 11 studies on orlistat and five studies on sibutramine and concluded that both appear to be modestly effective in promoting weight loss, but longer and more comprehensive studies are still needed.
• Another study, published in the December 2003 International Journal of Obesity and Related Metabolic Disorders, found that orlistat, when combined with lifestyle changes, effectively reduced weight among Mexican-American women, a population at high risk for obesity. In this study, 56 women were randomized to receive orlistat, behavior modification, a low-fat diet, and moderate physical activity for one year, while 52 women were randomized to a wait list control group. This is a small number of test patients, and the benefit of orlistat could not be isolated from the benefits of a low-fat diet, physical activity, and behavior modification.
• Researchers have also found that sibutramine may help with maintaining the weight after the pounds have come off—often the toughest part of successful weight loss. The study, published in the August 2003 American Journal of Clinical Nutrition , followed 261 individuals for 18 months after a six-month weight loss phase. The amount of weight initially lost, physical activity, and taking sibutramine all increased the likelihood of maintaining weight loss.