FDA Warning for ondansetron and metoprolol

The US FDA has put a class of antiemetic drugs, including ondansetron on its latest quarterly list of products to monitor because of potential signals of an increased risk for serotonin syndrome.

The beta blocker metoprolol succinate also landed on the list because of reports that suggested therapeutic ineffectiveness.

Appearance on the watch list does not mean that the agency has concluded that the drug poses the health risk reported through FAERS. What it does mean is that the FDA will investigate whether there is a causal connection.

The antiemetics on the watch list belong to a subtype of serotonin blockers that bind to the 5-HT3 receptor. Serotonin syndrome is caused by excessive levels of the neurotransmitter. It can be fatal. Symptoms include confusion, agitation, dilated pupils, headache, rapid heart rate, and changes in blood pressure and temperature.

Product name: active ingredient (trade) or product class	Potential signal of a serious risk/new safety information	Additional information (as of May 1, 2013)
Metoprolol succinate extended-release products	Lack of therapeutic effect, possibly related to product quality issues	FDA is continuing to evaluate this issue to determine the need for any regulatory action.
Serotonin-3 (5-HT3) receptor antagonist products: ondansetron, palonosetron	Serotonin syndrome	FDA is continuing to evaluate this issue to determine the need for any regulatory action.