TRENTON, N.J. -- Shares of drug maker Merck & Co. dropped 2.5 percent in heavy trading yesterday, a day after medical journal reports offered fresh ammunition to patients suing over its withdrawn painkiller Vioxx.
The reports also raised new concerns about whether Arcoxia, which Merck had planned as a successor to Vioxx, is safe enough to be allowed on the US market.
Shares of Merck, which faces more than 16,000 lawsuits over Vioxx, dropped more than 3 percent during the day but recovered slightly. About 12.25 million shares traded hands, nearly double the normal daily volume.
The reports were posted Tuesday on the Journal of the American Medical Association website, ahead of their scheduled Oct. 4 print publication, due to ``public health implications" of data on the safety of several painkillers.
The reports reviewed dozens of studies, involving hundreds of thousands of patients, of Vioxx and other anti-inflammatories.
One found the Merck drug increased risk of heart attack and stroke immediately -- not after 18 months of use as the company has insisted publicly and in courtrooms. That review also found that Vioxx was particularly dangerous at doses higher than 25 milligrams per day.
The second review showed that Vioxx increased the risk of kidney problems about 50 percent and nearly tripled the risk of potentially deadly abnormal heart rhythms.
Merck lost its first Vioxx trial in August 2005 when jurors decided a heart attack triggered by a Vioxx-induced blood clot caused a fatal irregular heartbeat in a Texas man; the verdict and the jury's $253 million award are being contested by Merck.
``This is the most devastating thing for Merck's defense," analyst Steve Brozak of WBB Securities said of the JAMA reports and an accompanying editorial.
Merck said the ``interpretations" and editorial in JAMA are contradicted by previous, more reliable studies .
The FDA is currently reviewing data on Arcoxia to decide whether to approve it. Merck said it has not decided whether to pursue asking the FDA to allow it to resume Vioxx sales.