Rimonabant: A New Approach to Diet Pills

Thursday, June 21, 2007 - 5:25pm

By John Messmer, MD

In the never ending search for a pill to help with weight loss, research has found a new way to approach the science of appetite suppression. It is common knowledge that marijuana makes people hungry. They call it "the munchies" because the active ingredient, THC, in addition to causing euphoria, stimulates the appetite. Because it also reduces nausea, some states allow it to be prescribed to treat chemotherapy-induced side-effects and the wasting that can accompany AIDS. A similar compound, dronabinol, has been used as an anti-nausea and appetite stimulation medication also. These drugs, called cannabinoids, attach to cannabinoid (CB) receptors throughout the brain with a variety of effects.

Blockage of cannabinoid (CB) effects

If stimulating a CB receptor increases appetite, the logical conclusion is that blocking it will reduce appetite. Rimonabant, available in Europe since 2006 under the name Acomplia, was just reviewed by the FDA for just such a use. There are two known types of CB receptors. Rimonabant blocks the CB1 receptor and has resulted in about a 5 percent weight loss on average with improvements in diabetes and cholesterol. It has the added effect of reducing the desire for nicotine in smokers.

The downside of Rimonabant

Sounds like a great idea, right? Well, to keep the appetite suppressed, it must be continued - possibly for life, or the weight returns. When marijuana stimulates CB receptors, it induces euphoria and reduces nausea. Rimonabant, by blocking the receptors, can cause depression, anxiety, and nausea. In fact, the FDA has delayed its release in the U.S. because thoughts of suicide were more common in people taking rimonabant. It might not help to stop taking the drug if this happens since rimonabant stays in the body for at least two weeks after taking it.

The CB receptors are involved in a lot of our physiology. They have a part in heart and nerve function and possibly in protection from cancer and they affect pressure in the eyes. So far, it's not known if rimonabant will have any effects elsewhere in the body.

Weight loss: is Rimonabant worth it?

Even if it does get approved for use in the U.S., some doctors are concerned about the potential risks to get only a 5 percent weight loss, even if diabetes and cholesterol improve. In the meantime, there's still the old time, tried-and-true method of weight loss: Diet and exercise.