All makers of ondansetron hydrochloride (Zofran) are voluntarily pulling the 32mg, single IV dose from the market due to the risk of serious cardiac effects. The FDA is working with GlaxoSmithKline and manufacturers of the generic version — Baxter Healthcare Corporation, Hospira, Teva, Bedford Labs and Claris Lifesciences — to recall the product, and expects it to be removed from the market through early 2013.

The high dose formulation of ondansetron was indicated to prevent chemotherapy-induced nausea and vomiting. Lower doses of the drug are used to treat post-operative nausea and vomiting.

The FDA had previously warned about the drug, which is sold pre-mixed in solutions of either dextrose or sodium chloride in plastic containers, and further study has confirmed that the high dose of the drug can cause "a specific type of irregular heart rhythm called QT interval prolongation, which can lead to Torsades de Pointes, an abnormal, potentially fatal heart rhythm," says the FDA.

The agency continues to recommend the IV regimen of 0.15mg/kg administered every 4 hours for 3 doses, not to exceed 16mg in a day. Further, no single IV dose should exceed 16mg. The FDA says it can't recommend an alternative single-IV dose regimen.

The FDA doesn't "anticipate that removal of the 32mg intravenous dose of ondansetron currently sold as pre-mixed injections will contribute to a drug shortage of IV ondansetron, as the 32mg dose makes up a very small percentage of the current market," at less than 1% of sales.

Stephanie Wasek