Merck, the US pharmaceutical group, on Monday received a fresh blow to the defense of its painkiller Vioxx.
The New England Journal of Medicine, one of the world’s most prestigious medical journals, published a correction arguing that the risk of heart problems was elevated throughout the period that patients took the drug.
The journal took the rare step of issuing an online change to the pivotal Approve study for Vioxx it had previously published.
The study had only highlighted heart problems developing for patients with lower bowel tumors after 18 months of treatment with the drug.
The findings had been interpreted by some as suggesting that Vioxx was safe for short-term use, although critics of the drug had claimed instead that risks emerged with as little as four months’ use.
Merck took the surprise step of withdrawing Vioxx in September 2004, largely on the basis of a three-year study showing a heightened risk of heart attack and strokes for those on the drug for more than 18 months. In a letter in the journal, Dr Robert Bresalier of the University of Texas and Dr John Baron of Dartmouth Medical School, who wrote the original Merck-funded Approve study, conceded that there had been statistical errors in their analysis showing a difference between the drug’s use up to and beyond 18 months.
They stressed that their original article’s conclusion remained unchanged, notably that there was an increased risk of heart problems in patients taking Vioxx if they had a history of lower bowel tumours. The new analysis suggests health problems may have begun earlier but only become evident after 18 months.
Monday’s news failed to depress Merck’s share price, which rose slightly. But it comes at a sensitive time for the company, which is fighting more than 11,500 lawsuits brought by patients and families who claimed health problems linked to Vioxx.
Critics of the Approve study, such as Dr Steven Nissen from the Cleveland Clinic, who wrote a separate letter in the latest issue of the journal, said that Merck had used the claim of no risk until 18 months after usage began in their defense in the litigations.
Kamran Abbasi, editor of the journal of the Royal Society of Medicine and former acting editor of the British Medical Journal, said: “These findings affect the interpretation of the Approve study. The episode shows once again the limits on how much medical journals can do to police the system. The reality is that journals are at the whim of powerful companies and their research departments.”