Novartis Withdraws Ex-Lax, Plans New Form

The US Food and Drug Administration has proposed a ban on theover-the-counter sale of a common laxative ingredient, phenolphthalein, because of concerns that it may cause cancer. In response to this proposal, the Swiss pharmaceutical major, Novartis AG, has decided to pull most versions of its laxative product, Ex-Lax, from the US market.

At a recent FDA meeting, data from two-year animal carcinogenicity studies were presented (Marketletter June 9). The results demonstrated that rats and mice which were administered around 50 to 100 times the normal human dose of phenolphthalein developed a variety of tumors, while other studies have shown that in mice fed up to 30 times the recommended human dose, both tumors and genetic damage was noted.

Although epidemiological human data have not revealed any reports of cancer related to the use of phenolphthalein in humans (Ex-Lax has been available on the market for nearly 100 years), the FDA said that animal studies indicate a potential cancer risk to people who use this product at higher than recommended doses or for extended periods of time. The agency has opened a 30-day comment period on the proposal to reclassify phenolphthalein as a category II ingredient - one not generally recognized as "safe and effective."