The increased heart risk from Vioxx, Merck & Co's withdrawn arthritis medicine, begins much earlier than after 18 months of use, according to a study that contradicts assertions by the drug maker and its scientists.

The 2,434-patient study, published on Wednesday in the New England Journal of Medicine, was halted early when the medicine was pulled from the market in September 2004.

Although the median duration of treatment was only 7.4 months, the researchers concluded that Vioxx, known generically as rofecoxib, was still associated with an increased frequency of adverse cardiovascular events.

Adverse events included fatal and nonfatal heart attacks, strokes, sudden death from cardiac causes, blood clots and chest pain, the study said.

Merck said the study in the Journal was just a small piece of the Vioxx story, and said it was not conclusive.

The study was limited by a relatively small number of adverse heart events -- 15 in the Vioxx group and 6 in the placebo group -- and its shorter-than-planned duration, the researchers said.

However, our findings suggest an increased risk of cardiovascular thrombotic events in patients randomly assigned to receive rofecoxib during or within 14 days after the treatment period, the researchers said.

Dr. David Kerr of Britain's University of Oxford was the lead author of the study.

MERCK RESPONDS

Merck spokesman Kent Jarrell said the study should not be taken out of context from the totality of all the data that's out there.

Jarrell added, It's very difficult to draw meaningful conclusions from the small number of cardiovascular events in this trial because it was prematurely terminated.

Merck pulled the formerly $2.5 billion a year pain drug after a different study showed it doubled the risk of heart attack and stroke in those who took it continuously for at least 18 months.

The company is facing more than 27,000 lawsuits from people who claim to have been harmed by the drug.

During trials, Merck's lawyers and company witnesses have insisted that there is no scientific evidence to suggest increased risks from shorter-term use. Opposing attorneys have asserted the risk begins well before 18 months.

Merck said preliminary data from this and other studies were available to lawyers on both sides since before the first Vioxx case was tried. There has been testimony in many trials concerning the data from these studies, Jarrell said.

While the analysis of the shortened study found a statistically significant higher risk of adverse heart events among the Vioxx patients, there was no statistically significant difference between the Vioxx and placebo groups during the 24 months following closure of the trial, researchers found.

The study had been designed to show whether Vioxx could reduce the recurrence of colon cancer following surgery and chemotherapy or radiation treatment.

Overall, four patients in the Vioxx group and two in the placebo group died as a result of thrombotic events within 14 days after the treatment period. However during the 24 months follow-up period there were five deaths in the Vioxx group and seven from the placebo group, which was not deemed to be a significant difference.

Medicine