I have never prescribed weight loss medications to any of my patients and given the published studies, I don’t see myself ever prescribing them. Let me explain why.
There are five prescription medications approved by the FDA on the market for weight loss: phentermine, phendimetrazine, benzphetamine, sibutramine and orlistat. All but the last are sympathomimetic drugs meaning that they mimic the sympathetic nervous system – that is, they rev it up. They stimulate the release of norepinephrine or inhibit its reuptake by the nerve terminals.
Because of its effect on the central nervous system, these medications are used cautiously, if at all, in people who have the cardiac disease – from uncontrolled high blood pressure to coronary heart disease.
Because of their mechanism of action, phentermine, phendimetrazine, and benzphetamine are only approved for short-term use which is approximately 12 weeks. Sibutramine is the only approved sympathomimetic drug approved for long-term use (maximum of 2 years).
Sibutramine is currently under review by the FDA however, because studies show an increase in non-fatal heart attacks and strokes. I believe October 2010 is when the FDA is set to release its findings on whether the medication will be removed from the market. Of note, Europe’s FDA equivalent has suspended the use of sibutramine.
So just how effective are these medications? The sympathomimetic drugs cause at most about a 9.5# prescription medications for weight loss – not terribly significant when we’re talking about people with a body mass index (BMI) between 30 and 39 (obesity) or 40 or higher (extreme obesity).
A BMI between 30 and 39 for a woman who is 5’5″ tall means she weighs between 149# and 179#. This is officially considered “overweight”. If she weighs between 180# and 239#, she is officially obese. She is considered extremely obese if her weight is 240# or more.
A 6′ tall man weighing between 209# and 277# is officially classified as obese, while anything higher than 277# is considered extremely obese.
Since these medications are generally prescribed only for people who are obese or extremely obese, the 10# weight loss that one may get on these medications I feel isn’t sufficient to offset the potential harm.
Orlistat works differently: it blocks the absorption of fat so the fat is excreted in stools. (There is a limit to how much fat it can block). The common side effects reported are oily spotting, fecal incontinence, flatus with discharge.
The weight loss associated with orlistat is anywhere from 4.5# to 7.5#s. As with the other medications above, the weight is gained once the medication stops.
Weight loss for those who are obese or extremely obese involves more than taking a pill. As it is we are just beginning to understand the complex physiology of weight loss, the role of certain chemicals in satiety as well as the impact of genes. My patients are looking for long term solutions and frankly, the cardiac risks associated with sympathomimetic medications are not offset by the minimal weight loss.
