Rimonabant, known in the United States as Zimulti, is a weight loss drug that was approved for use in Europe in June of 2006, but has yet to be approved in the United States. Rimonabant is the first Cannabinoid-1 Receptor Blocker, a new line of obesity drugs that work by blocking the Canabinoid-1 (CB-1) receptor found in the brain and other organs. Blocking this receptor seems to decrease cravings for food while aiding in the metabolizing of both glucose and fats. As a result, less fat is stored in the body because the patient not only eats less but also metabolizes the food that is eaten properly. As a side benefit, those who are on Rimonabant are often able to stop smoking because the drug curbs the craving for nicotine in the same way in which it stops the craving for food. The drug was discovered and then developed by the Safino-Aventis pharmaceutical company.

Why Is Rimonabant not Approved in the United States?
Rimonabant has been very effective for patients who are looking to shed unwanted weight in Europe, yet the drug has not been approved for use in the United States. In fact, as of June of 2007, the Food and Drug Administration in the U.S. (FDA) has unanimously voted not to accept the drug in the United States without further testing. Their reasoning is that there are too many potentially dangerous side effects that have not been addressed.

In clinical trials, patients who were on the medication reported twice as many psychiatric problems after taking the drug than those taking a placebo. These problems included anxiety, depression, and insomnia. Some patients were more susceptible to suicidal thoughts, which was a major cause for concern to the members of the FDA advisory panel that was assessing the drug. The FDA was also concerned about approving the drug because of the intense market for anti-obesity drugs in the United States. The panel that studied the drug felt that the promise of weight loss would make many overweight consumers turn to the drug without considering the psychological risks.

Reason Behind the Side Effects

Part of the reason behind these potential side effects of Rimonabant is the way it affects the body. The CB-1 Receptor that is blocked by the drug is sometimes referred to as the “pleasure receptor.” When it is blocked, cravings for food are stopped because food does not bring the pleasure it used to bring. However, blocking the pleasure receptor has unknown consequences for the emotional and mental health of the patient, especially when done for a long period of time. For this reason, it is believed, some patients develop suicidal thoughts and dangerous depression. Mood swings are also a potential side effect. Two patients who were on Rimonabant for an extended period of time developed amnesia, which could have been from the drug.

The Rebuttal

While the FDA weighs the potential benefits and risks of this new weight loss drug, Sanofi-Aventis points out that the benefits far outweigh the potential risks. Patients who were on the drug during the clinical trials phase were able to lose 5% more weight than those who were on a placebo after a year. Even the FDA acknowledged that the drug produced meaningful weight loss results. The weight loss in these patients was often in the waist area, which is significant because too much excess weight in the abdominal area is a precursor to heart disease. Also, those who took Rimonabant lowered their blood glucose and blood pressure levels while increasing the good cholesterol in their bodies.

While depression is a potential side effect of the drug, the number of patients who experienced severe depression was small, and those patients could have had a tendency towards depression that had not been diagnosed prior to taking the drug.

Another argument in favour of the drug is its intended use. Like surgical obesity treatments, Rimonabant is intended only for those patients whose obesity is causing them serious physical problems, such as heart disease. In fact, the European Medicines Agency only approved the drug to be used for patients with a body mass index of at least 30. For significantly obese patients who have tried traditional weight loss options without success, the potential side effects of weight loss drugs like Rimonabant may be an acceptable risk in comparison to potentially fatal medical conditions caused by obesity.

Will Rimonabant Be Approved in the United States?

At this point, it is unclear whether or not the drug will be approved for use in the United States. The FDA is waiting to see more long-term studies on the side effects of the drug in order to gain a more thorough understanding of what patients on this drug are truly risking. Sanofi-Aventis and the FDA are currently discussing what needs to be done to proceed with the application for approval. While the drug has not yet been approved, there is still hope that a future approval may happen, which is good news for those unsuccessfully fighting their battle with obesity.