In a rare move, The Food and Drug Administration rejected the vote of its own advisory panel to ban a widely-prescribed narcotic painkiller, propoxyphene, but the agency has ordered the drug’s manufacturer to add stronger, boxed warnings to labels about the dangers of overdose.

“Based on all evidence available to the agency, FDA has concluded that the benefits of propoxyphene for pain relief at recommended doses outweigh the safety risks,” an agency statement said.

An advisory panel voted 14 to 12 to ban the drug propoxyphene, the main ingredient in the painkillers Darvon and Darvocet, citing reports of thousands of deaths tied to the drug since its approval in 1957. Physicians at that hearing also testified that metabolites of propoxyphene are toxic to the heart and may accumulate in the body.

In a statement released to the public, officials said “FDA recognizes that there are unanswered questions about the safety of propoxyphene when used at doses higher than recommended on the label. These unanswered questions include the effects on the heart in overdose.”

Along with the labeling changes, the agency said it would require the drug’s manufacturer to conduct a safety study of the effects of propoxyphene on the heart and said it would work with other federal health agencies, such as the Department of Veterans Affairs and the Centers for Medicare and Medicaid Services, to conduct additional studies of the medication’s safety compared to other painkillers.