Three commonly used drugs - Prozac, Xenical and Meridia - may help type 2 diabetes patients lose small amounts of weight, although long-term benefits are not clear, a new review of 22 studies suggests.
Prozac and Sarafem, known generically as fluoxetine, are most commonly prescribed as antidepressants. Xenical, the brand name for orlistat, blocks fat digestion in the intestines. Meridia, known generically as subtramine, is an appetite suppressant that works in the brain.
According to the systematic evidence review by Dr. Susan Norris of the U.S. Centers for Disease Control and Prevention and colleagues, patients taking fluoxetine had lost an average of 11 pounds (5.1 kilograms) 24 to 26 weeks after starting the therapy. Patients taking orlistat had lost an average of four and a half pounds (two kilograms) 12 to 57 weeks later, and those taking sibutramine had lost an average of 11 pounds 12 to 52 weeks later.
“The magnitude of weight loss is modest, however, and the long-term health benefits remain unclear,” the review concludes.
Side effects of the therapies included oily bowel movements for those taking orlistat; sweating, tremors and drowsiness among fluoxetine users; and heart palpitations in some sibutramine patients.
Although the researchers acknowledge that long-term weight loss is “of paramount importance,” they say their review could help determine how weight loss drugs should fit into the overall picture of type 2 diabetes care.
“For example, if weight loss can be demonstrated with drugs in the short term, pharmacotherapy may be combined with behavioral interventions for long-term weight control,” Norris says.
The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Although a variety of other weight loss drugs exist, only 22 randomized controlled studies of fluoxetine, orlistat and sibutramine met the high standards set by the researchers for inclusion in the review.
Of the 22 studies reviewed, the drugs’ manufacturers paid for 18 of them and did not provide the reviewers with unpublished studies the companies had done on each of the included drugs, Norris says.
Norris says there is only a small amount of data on other weight loss drugs and people with type 2 diabetes. For instance, the researchers did not find any good studies examining the effects of popular weight loss drugs like ephedra in diabetic patients.
Obesity has been closely linked with type 2 diabetes. In a 2000 study, 80 to 90 percent of people with type 2 diabetes are overweight. Obesity may also worsen problems associated with diabetes, including high blood sugar, high cholesterol and high blood pressure, say Norris and colleagues.
Norris says people with diabetes who are also overweight may have a harder time losing weight than non-diabetics.
Insulin therapy itself might cause weight gain, Norris says. Keeping track of a complex series of treatments for diabetes, high cholesterol and high blood pressure “all complicate behavioral change aimed at weight reduction.”
Recommendations by the American Diabetes Association in 2002 say that weight loss drugs may be useful in treating obesity among type 2 diabetes patients, but also note that “these drugs work best in conjunction with lifestyle strategies” such as low fat diets and increased exercise.
Norris and colleagues say more research is needed to find out whether weight loss drugs work better when combined with diet and exercise changes.
“In general populations, drugs have been combined with various lifestyle interventions, but most [drug] trials include relatively weak lifestyle programs, perhaps in part to better reveal the medication effects,” Norris says.