Currently, 120 deaths associated with the patches are under federal investigation.
The FDA believes accidental overdoses are a recurring problem because the patches contain a high concentration of the controlled substance.
The investigation aims to distinguish whether the deaths are a result of inappropriate use, or if it's the product's quality to blame.
FDA's Dr. Robert Meyer says, at least some may have been accidental overdoses, and reports suggest patients or prescribers weren't aware of crucial safety information on the drug's label,
The patches were first approved under the brand name Duragesic in 1990, and a generic version hit the market in February. FDA has reports of death among users of both, Meyer told the Associated Press. It's not unusual to receive increased side-effect reports shortly after a new product reaches consumers, he said.
