WASHINGTON – There were preliminary indications of heart problems with the painkiller Vioxx before it was withdrawn, but it was difficult to sort through conflicting data, a health official said yesterday at the opening of hearings on the risks of popular painkillers.

“We were not asleep at the wheel, we were actually engaged in reviewing a lot of data,” Dr. Lourdes Villalba told a joint meeting of the Food and Drug Administration’s arthritis advisory committee and its drug safety and risk management advisory committee, which are looking into Vioxx, Celebrex, and Bextra.

Vioxx was pulled from the market September 30 by manufacturer Merck & Company, after a long-term study showed a higher rate of strokes and heart problems in people using the drug.

Related drugs Celebrex and Bextra, made by Pfizer Inc., remain on the market, though some studies have also indicated they, too, may carry an added heart risk.

Dr. Villalba, the medical officer responsible for Vioxx at the FDA’s Center for Drug Evaluation and Research, pointed out that a study done in 2000 comparing Vioxx with the painkiller naproxen showed a higher rate of heart problems with Vioxx, but other studies had conflicting results. In discussions with Merck officials, she said, the company suggested naproxen might have a heart protective effect.

Nonetheless, in 2002 the agency required an added warning on the Vioxx label urging caution in prescribing it for people with heart conditions.

“We never bought the naproxen theory,” she said, and Merck officials said they no longer make that argument.

Pfizer Vice President Dr. Joseph Feczko said the reports of increased heart problems need to be seen in context, considering that the drugs, known as Cox-2 inhibitors, have an important benefit: they reduce the sometimes serious stomach and intestinal problems that occur with many painkillers.

Dr. Kenneth Verberg, Pfizer vice president for inflammation and immunology, defended Celebrex as safe, though he said there is little data on use of the drug for more than one year. Further long-term testing of Celebrex is needed, he said.

Earlier, Dr. Ned S. Braunstein, senior director of Merck Research Laboratories, reported that the biggest increase in heart problems occurred after 18 months of use.

Dr. Garrett FitzGerald of the Department of Pharmacology at the University of Pennsylvania School of Medicine told the committees that, considering the hazard reports, similar new drugs may have to face tougher testing to win approval and those on the market ought to be put through the same new testing to retain approval.

Dr. FitzGerald told the panels that, just as low-dose aspirin affords heart protection and a small but definite risk of stomach and intestinal problems, so the Cox-2 inhibitors “afford gastrointestinal protection and a small but absolute risk of cardiovascular events.”

The two committees are holding a joint three-day session to gather data on the safety of the drugs and to make recommendations regarding their future use.

Recommendations could range from limiting these drugs to people not known to be at risk of heart problems, reducing the dose or duration of use, requiring tougher warning labels, and even taking the drugs off the market.

As the session began, the FDA promised prompt action on recommendations from advisory committees.

Dr. Steven Galson, acting director of FDA’s Center for Drug Evaluation and Research, reminded the committees that the drugs in question are important painkillers widely used by people in chronic pain. It is important to balance the risks of drugs with their benefits, he said. A drug that has a positive risk-benefit balance for the population as a whole, Dr. Galson added, may still cause serious problems for some individuals.

The FDA has been criticized for being slow to recognize problems with these drugs. However, committee chairman Dr. Alistair Wood of Vanderbilt University stressed as he opened the session that the committee “is not here to delegate blame or revisit the past.”