Merck

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reiterated Monday that clinical trials show its arthritis drug Arcoxia poses the same cardiovascular risk as a popular older pain reliever.

The company also again said it expects to hear from the Food and Drug Administration in late April on its application for Arcoxia, a cousin to the pain reliever Vioxx that Merck pulled from the market for heart-safety reasons in September 2004.

Merck's comments came as the company unveiled clinical-trial results that show a similar risk of cardiovascular blood clots between Arcoxia and diclofenac, a now-generic pain reliever. Merck says diclofenac is largest-selling pain reliever in the world. Diclofenac is sold under the brand name Voltaren by

Novartis

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.

The Whitehouse Station, N.J., drugmaker's remarks about the FDA review as well as the clinical trial results essentially repeat the company's Nov. 10 announcement. Now though, the company is providing more details about its Arcoxia study at the American Heart Association's annual scientific session and at an annual meeting of the American College of Rheumatology.

A study known as MEDAL said Arcoxia patients had 1.24 cardiovascular clots per 100-patient years, while diclofenac patients who had 1.30 clots per 100-patient years. The difference wasn't significant. The rate of heart attacks -- 0.43 per 100-patient years for Arcoxia and 0.49 per 100-patient years for diclofenac -- also wasn't statistically significant.

MEDAL also examined gastrointestinal risk. Stomach bleeding and ulcers are a worrisome side effect, especailly among the elderly, for medications like diclofenac, which are known as nonsteroidal anti-inflammatory drugs, or NSAIDs. Developers of COX-2 drugs have been trying to convince regulators of the stomach-protection quality of these drugs, but the FDA only approved this claim for Vioxx.

Additionally, the comparison trial found that there was a "significantly higher" rate of Arcoxia patients dropping out of the test due to high-blood pressure than diclofenac patients. The higher rate was detected among Arcoxia patients taking either 60 milligrams or 90 milligrams a day. Last week, Merck said it would ask the FDA to approve Arcoxia as a 30-milligram or 60-milligram treatment.

MEDAL didn't include patients who had been give a placebo. Merck said such a strategy for a long-term test for treating arthritis would have been unethical. MEDAL combined the results of three clinical trials conducted at 1,380 sites in 46 countries. The tests enrolled 34,701 patients, and the average treatment was 18 months.

The primary goal of the MEDAL test was to determine that Arcoxia did no worse than diclofenac in causing cardiovascular blood clots among patients who had osteoarthritis -- joint degeneration -- or rheumatoid arthritis, an inflammatory disease.

Last week, Merck said it would seek FDA approval for Arcoxia only as a treatment for osteoarthritis but would consider applications for other indications in the future. U.S. law permits doctors to prescribe a drug for any use once the FDA has approved it for a single disease or condition.

Like Vioxx, Arcoxia belongs to a class of drugs known as COX-2 inhibitors. Arcoxia is available in 62 foreign markets. Merck pulled Vioxx in September 2004 after a company-sponsored clinical trial revealed a higher cardiovascular risk among people who took the drug for more than 18 months. The company is now facing thousands of lawsuits by former Vioxx users who claim the drug caused them to have health problems.

Merck sought FDA approval for Arcoxia in late 2003. The agency granted conditional approval in October 2004, asking for more clinical-test data. Merck is sending its latest research to the FDA, to regulatory agencies in countries where Arcoxia is available and to regulators where Merck is seeking approval. The only COX-2 drug in the U.S. is

Pfizer's

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Celebrex.