Pfizer Inc. said Monday it plans to sponsor a major clinical study to further assess the cardiovascular safety of its arthritis drug Celebrex following the withdrawal of Merck & Co.‘s Vioxx, a drug in the same class.

Pfizer said that it was confident that Celebrex does not pose a heart risk based on its experience in multiple studies over several years and said some small trials suggest the drug may protect against certain heart problems.

The study will specifically look at inflammation and cardiovascular events in osteoarthritis patients at high risk for heart disease. The study will enroll more than 4,000 patients who have had a recent heart attack and who also have a history of osteoarthritis. The trial will last at least two years.

Pfizer (up $0.25 to $28.75, Research), whose shares rose in early trade on the New York Stock Exchange, said it will discuss the study design with the Food and Drug Administration and other regulatory agencies before finalizing its details.

Like Merck’s (up $0.11 to $30.61, Research) Vioxx, Celebrex is a COX-2 inhibitor and is approved to treat arthritis pain. A recent trial showed Vioxx doubled the risk of heart attack and stroke in patients who took the drug for more than 18 months, casting a cloud over all drugs in the class.