The increased cardiovascular risk from Merck & Co’s now-withdrawn painkiller Vioxx (rofecoxib) is seen before the 18 months previously thought to be the benchmark, according to a new study published in the New England Journal of Medicine.

The study included 2,434 patients with colorectal cancer who had had their tumour removed and were receiving the $2.5 billion a year Vioxx to reduce the risk of disease recurrence, but was terminated early when the medicine was pulled from the market in September 2004 after being linked to a doubling in the risk of heart attack and stroke when taken for longer than 18 months. The researchers continued to examine any cardiovascular thrombotic events reported up to 24 months after the trial’s close.

Median treatment duration just 7.4 months

Despite the median duration of active treatment being just 7.4 months, the investigators still found an increased frequency of adverse cardiovascular events – including fatal and nonfatal heart attacks, strokes, sudden death from cardiac causes, blood clots and chest pain - amongst the 1,167 patients receiving Vioxx. Of the 23 confirmed CV events, 16 occurred among Vioxx receivers during or within 14 days after the treatment period, and six patients died (four in the Vioxx group). During the two-year follow-up, 14 more patients (including six in the Vioxx group) suffered an event, one Vioxx patient died from cardiovascular causes, as did a further five given placebo.

Merck has stressed that it is difficult to draw any conclusions from this trial because of its short duration and the fact that it was terminated early. It also noted that the total dataset for Vioxx should be taken into account in determining its safety profile. Earlier this week, the company revealed it is facing more than 27,000 lawsuits from people who allege harm from the drug. It has always stressed there is no scientific evidence to suggest an increased CV risk prior to 18 months, so any indication to the contrary will not be welcome.