Drug company Pfizer Inc., the maker of Celebrex, will pay for an international study of 20,000 people.

The study will compare the potential heart risks of cox-2 inhibitor Celebrex to traditional anti-inflammatories by comparing the drug to two generic NSAIDs, the anti-inflammatories Naprosyn and Ibuprofen.

At present Celebrex is the only cox-2 inhibitor still on the market as both Vioxx and Bextra were withdrawn in 2004 over concerns of cardiovascular risks.

Cox-2 inhibitors were originally designed to be gentler on the stomach than non-steroidal anti-inflammatory medications.

In the study participants from the United States, Eastern Europe, Canada, Australia and South America will be randomly assigned to get one of the three drugs, along with a drug to prevent stomach irritation.

The participants will all have had a problem such as a heart attack or blocked arteries, or diabetes.

Neither the participants nor their doctors will know who is taking which drug, but both the drugs and the two year period of monitoring will be free.

The study will be led by Dr. Steven Nissen, a cardiologist at the Cleveland Clinic who was the doctor who first called for research on the heart risks of Celebrex and Vioxx in 2001.

The study will look into the risks of heart attack, stroke and death.

Nissen says that as so many people with arthritis are at risk of heart disease, it is important to know the cardiovascular safety of pain relief drugs.

Apparently independent researchers will collect the data and control the results, and Pfizer has promised that all results will be made public.

It has also promised that no senior authors will have financial ties to manufacturers of pain drugs.