The jury debating whether Merck & Co is liable for punitive damages in the latest Vioxx court case adjourned yesterday without reaching a verdict, leaving the US drugmaker biting its nails overnight.

Deliberations will continue later today in second phase of the case, which has already seen one man awarded $4.5 million in compensation, after the jury agreed with his claim that Vioxx (rofecoxib) made a significant contribution to a heart attack he suffered.

Merck pulled Vioxx off the market in September 2004 after a study showed the COX-2 inhibitor, which had sales of $2.5 billion a year at its peak, doubled the risk of heart attacks and strokes when taken for 18 months or more.

The 77-year-old man awarded damages, John McDarby, claimed to have taken the painkiller for four years. A second man, Thomas Cona, had a claim for compensation denied by the jury. Cona said he had taken Vioxx for 22 months, but his medical records could only prove usage for seven.

The jury is now deciding whether to award punitive damages against Merck, which would be limited to five times the compensatory damages under state capping laws, or $22.5 million.

To win punitive damages attorneys will have to prove that Merck intentionally misled the US Food and Drug Administration and that deliberately ignored or hid evidence of Vioxx’ ability to do harm. In the first phase of the study, the jury decided that Merck had failed to inform consumers and physicians of the risks associated with Vioxx’ use.

Central to the deliberations in the second phase is an analysis of clinical trials carried out by Merck in 2000 which revealed a higher incidence of heart attacks among patients on Vioxx compared to other drugs. Portions of this analysis were not submitted to the FDA, according to lawyers representing the plaintiff. Merck has argued that the analysis was preliminary and imperfect, was not required to be submitted to the FDA, and in any case the agency had access to all the data on which it was based.

Whatever the outcome of the second phase of the trial, Merck has leave to appeal the compensatory damages as well as any punitive damages that arise in the case, and analysts said it is hard to gauge any financial liability for Merck until these appeals have taken place.