A peer review for the New England Journal of Medicine (NEJM) broke confidentiality rules and leaked a damaging report about the blockbuster diabetes drug Avandia to the drug's manufacturer weeks ahead of publication.

The reviewer, Steve Haffner of the University of Texas Health Service Centre at San Antonio commented, "why I sent it is a mystery. I don't really understand it. I wasn't feeling well. It was bad judgement."

Avandia came under heavy scrutiny last year, after the NEJM published an analysis of the drug's efficacy and safety, which showed that the drug increased the risk of heart attack by 43% in people who took it for at least 23 weeks. The report garnered widespread media attention, prompted the US Food and Drug Administration to issue a safety alert, and cut the stock price of Avandia's manufacturer, GalaxoSmithKline (GSK) by 13%. In 2007, sales of Avandia were down 38% from a year earlier worldwide.

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