Pfizer study shows risk of cholesterol pill switch

VIENNA (Reuters) - Patients switching from Pfizer's branded cholesterol pill Lipitor to Merck & Co's Zocor -- now available as a cheap generic -- are more likely to have a heart attack or die, according to a Pfizer-backed study.

The findings, which were based on observations from a primary case database in Britain, were presented at the annual European Society of Cardiology congress on Wednesday and will fuel controversy about drug switching.

The British drug industry said in July it planned to launch a legal challenge to moves by the state-run National Health Service to switch large numbers of patients onto cheap generics. Drugmakers argue such schemes are potentially unsafe.

Pfizer's study covered records from 1997 to 2005 and compared outcomes for 2,511 patients who took Lipitor for six months and then switched to simvastatin -- the generic name for Zocor -- with 9,009 who stayed on Lipitor.

The conclusion was that switching was associated with a 30 percent increase in the relative risk of major cardiovascular events, including heart attacks, strokes and death.

The reasons for switching were not given and patients were not randomly assigned to each arm of the study, limiting its significance. Nonetheless, Pfizer said it raised concerns.

Peter Lansberg of the University of Amsterdam's Academic Medical Centre, one of the investigators, said the difference was not surprising since Lipitor was known to be more potent at lowering levels of harmful cholesterol in the blood.