Contamination Alert

EMEA, the European regulatory authority, has taken the unusual step of ordering the withdrawal of all batches of Roche's anti-HIV medicine Viracept (nelfinavir) after product containing traces of contamination were found on pharmacy shelves.

The drugs were manufactured in the company's Swiss plant and were found to contain small quantities of ethyl mesylate, a DNA-alkylating agent that can cause cancer. According to a Roche spokeswoman, the ethyl mesylate had been used to clean the reactor vessels. The contamination has been put down to human error, and investigations into precisely what went wrong are under way.

Because there are insufficient data on what levels of ethyl mesylate are safe, EMEA has asked Roche to carry out toxicology experiments on the substance in rats. The company is also setting up a registry of all patients who conceivably could have been affected by contaminated batches of the drug, and it will monitor them on an ongoing basis. This includes all those who have taken product from any of the batches released since March, plus any pregnant women or children who have ever taken the drug, including infants who had been exposed to it in the womb. Lower levels of ethyl mesylate have been found in older batches, and Roche is now identifying precisely which batches of the drug are affected.

Patients have been switched to alternative protease inhibitors. Packs of Viracept in North America and Japan -- where the drug is marketed by Pfizer and Japan Tobacco, respectively -- were unaffected, as they were not manufactured in the Swiss plant.

The Roche spokeswoman says EMEA will have to reinspect the manufacturing process before the product is allowed back on the market.