In a move that could affect millions of people who take over-the-counter constipation remedies, the Food and Drug Administration is reviewing reported cancer-causing effects of a common laxative.
The review of phenolphthalein was provoked by a government study that showed it to be carcinogenic in laboratory animals.
The chemical is the active ingredient in Ex-Lax and some other laxatives. It caused cancer in rats and mice, said officials of the National Toxicology Program (NTP).
Typical of such studies, the animals were given doses of phenolphthalein (pronounced feen-ol-THAY-leen) far in excess of the amount humans take in laxative preparations.
A spokesman for Sandoz Pharmaceuticals Corp., which manufactures Ex-Lax, said the company is cooperating with government agencies in follow-up studies.
Meanwhile, officials of Schering-Plough Corp. said that as soon as preliminary results from the NTP studies came to the company’s attention, it reformulated its two principal phenolphthalein-containing laxatives, Correctol and Feen-a-Mint, to remove the chemical.