From the data that continues to accumulate, it appears that “so far so good” is the watchword with rimonabant. However, several observers at the AHA meeting urged caution. There are two very good reasons not to get too excited about this drug just yet. First, rimonabant is the first of a new class of drugs targeting the endocannabiniod system, which helps to regulate pleasure, relaxation, and pain tolerance. We still do not have a good notion of what happens when we interfere with this system on a very long-term basis (and from this new study, it seems obvious that treatment with rimonabant will have to be chronic.) The fact that significant depression was seen in at least some of the patients enrolled in the trials so far ought to raise a fair amount of caution. Further, neurologists point out that the endocannabinoid system helps to protect the brain under some circumstances (such as stroke and head injury,) and some worry that brain damage in these circumstances might be worse in patients taking drugs that block the endocannabiniod system. Even more scary, a recent article in the journal Multiple Sclerosis describes a patient whose previously subclinical case of multiple sclerosis became active when this drug was started.

In the trial, however, patients who took 20 mg rimonabant for 1 year were then re-randomized to either continue on rimonabant, or to switch to placebo. Patients who stayed on rimonabant for the second year maintained the same degree of weight loss (they did not lose additional weight,) while those switched to placebo gained weight. At the end of 2 years, patients who took rimonabant for one year and placebo for the second year had about the same amount of overall weight loss as patients who took placebo from the beginning.

Side effects included depression, anxiety and nausea. About 1 in 8 patients taking rimonabant dropped out of the study due to side effects.