The trial is currently under intense scrutiny following the fiasco over Vioxx. Its withdrawal, after concerns over its safety, had cast doubt over the entire class of drugs known as COX-II inhibitors of which it was a member.
Launched in 1999, Vioxx became one of the most heavily promoted prescription drugs, and was marketed in 80 countries with annual sales of $2.5bn (€1.9billion). It was withdrawn after patients taking it for at least 18 months suffered twice as many heart attacks or strokes as those taking a placebo.
As a direct competitor to Vioxx, Pfizer's Bextra is likely to be the recipient of unwanted attention surrounding the COX-II inhibitors. Although full data is not available, two studies using the pill and an injectible version of the same drug as painkillers for patients undergoing open-heart surgery have now shown it raises the risk of new heart attacks.
Pfizer's other COX-II drug Celebrex may fare better, emerging from this latest situation relatively unscathed. Last week they announced that it was setting up a trial which would include examination of the cardiovascular safety of the drug, Celebrex.
Celebrex closely resembles chemically, a 50-year-old glaucoma drug that works by reducing blood pressure in the eye. If part of Celebrex's chemical structure actually lowers blood pressure, that could explain why so few heart safety issues have emerged for this drug.
Pfizer's new two-year global study will enroll more than 4,000 patients who have had a recent heart attack and who also have a history of osteoarthritis, the most common form of arthritis in which the joints are harmed by wear and tear.
If the trial is successful, it could help ensure the continued success of Celebrex, which had 2003 sales of $1.9 billion. If it fails, it could jeopardize not only Celebrex but also Bextra.
The Cox-2 inhibitors were launched in the late 1990s and were claimed to have powerful painkilling properties without damaging the stomach, which can happen with ordinary painkillers such as aspirin and ibuprofen.
However, long-standing concerns culminating in the Vioxx scandal have placed an intense spotlight on the class of drug of which its future now remains unclear.