It looks like Merck & Co’s painkiller Arcoxia could face an uphill battle when it goes up in front of a US Food and Drug Administration advisory panel on Thursday.

The agency’s arthritis advisory panel will review the COX-2 inhibitor Arcoxia (etoricoxib) and decide whether to give it the green light of approval for treating the signs and symptoms of osteoarthritis but in documents posted to the FDA website, agency staff questioned the safety of the drug.

In briefing documents, FDA staff stated that data from the MEDAL trial showed that the risk of cardiovascular events in patients who received Arcoxia was "comparable" to those who received the older non-steroidal anti-inflammatory drug diclofenac. However, the findings also revealed that those taking Arcoxia had a higher incidence of elevated blood pressure, congestive heart failure and oedema, compared with those taking diclofenac.

The staff noted that "a new product that appears to have an increased overall risk profile for cardiovascular disease...would not be appropriate for marketing unless the product fills an unmet medical need."

The meeting on Thursday will be well-watched, coming as it does in the wake of strenuous criticism levied at the agency after Merck's multi-billion-dollar forerunner Vioxx (rofecoxib) was pulled off the market in 2004. Arcoxia is already sold in 63 countries and brought in $265 million last year, and Merck is still confident of getting the go-ahead from the agency, despite the general consensus that this will not be the case.

The company said Arcoxia was less likely to cause gastrointestinal problems such as bleeding that can be complications from NSAIDs and its risks were consistent with other drugs in the class.