Well, things usually come in Pairs.....
The Law of Two's -- I call it. Of course, it doesn't apply to your most common diagnoses. It only applies to things you only see once every month or less often. It has to be something you wouldn't normally diagnose on a routine week. Once it becomes routine, it is beyond the law of two's. And that's how the law works (if you want to believe in it).
Well, this past week, the FDA took Zelnorm temporarily off the market as it seeks to redefine its roll in treating IBS patients, given the newly confirmed cardiovascular risk profile.
Today, comes another announcement for another drug, Pergolide, used uncommonly in patients with Parkinson's disease (given the availability of newer drugs), that has been taken off the market. This decision was based on two case-control studies published in the NEJM on January 4th, 2007 that showed that the medication, a dopamine agonist, was implicated in valvular dysfunction due to a histologically distinct form of valvular fibrosis. The mechanism of pathology is due to the drug's activation of a serotonin receptor, the 5-hydroxytryptophan-2B receptor. In contrast, Zelnorm is a partial 5-HT4 receptor agonist with moderate affinity for the 5-HT1 receptor. These receptors are having some activity on the heart muscle, its vasculature or the heart valves themselves. I find it interesting that serotonin receptors have been implicated in two drugs that have been removed from the market this week. Hey, maybe the law of two's does work.
The other interesting fact is that depressed persons have higher rates of acute cardiac events. Again, is serotonin implicated here? I don't know whether this statistic relates to depressed patients on anti-depressants or off of them. It is something to explore.
Read the FDA Public Health Advisory for more information on the Pergolide withdrawal.