Merck & Co’s share price soared by as much as 13% during afternoon trading on the New York Stock Exchange on Friday after a US Food and Drug Administration advisory panel ruled that the company’s COX-2 inhibitor, Vioxx (rofecoxib), which it voluntarily withdrew from the market after it was linked to an increased risk of heart attack [[01/10/04a]], could return to the market. The news came after the panel concluded that all three medicines under scrutiny – Vioxx, and Pfizer’s COX-2 offerings Celebrex (celecoxib) and Bextra (valdecoxib) – posed some degree of heart risk, voting 17 to 15 that Vioxx’ overall risk-benefit profile supports marketing in the US.

Although investors have clearly welcomed the vote, almost the same number of panel members voted against returning the product to the market. The committee also voted 17 to 13 with two abstentions that Bextra should remain on the market, while Celebrex was backed by a staggering 31 votes to one as the group clearly felt that the drug was at the lower end of cardiovascular side effects. Although some members expressed concern over the product at higher doses, the news will please Pfizer, which has continued to defend Celebrex in light of negative clinical trial data and calls for the drug’s market withdrawal [[04/10/04c]], [[20/12/04a]], [[02/02/05b]].

However, all three COX-2s could come with a “black box” warning – the strongest available – to highlight the cardiovascular risk. European regulators have also revealed a number of “urgent safety restrictions” for the drugs [[18/02/05a]]. The panel also recommended warnings, although not necessarily a black box, for all non-steroidal anti-inflammatory agents, including over-the-counter medications such as ibuprofen, regarding a potential class effect on cardiovascular function.

Whether Vioxx ultimately does return to the market remains to be seen. The panel ruled that stronger warnings should be applied to Vioxx if it were to be re-launched, and it could potentially be restricted to second- or third-line use. Many committee members also said that re-introduction should be limited to a 12.5 mg dose rather than the previously marketed 25 mg to 50 mg doses. Late last week, Merck said that it would consider re-introducing Vioxx onto the market [[18/02/05b]].