WASHINGTON • The Food and Drug Administration is warning patients about a potential mix-up between powerful prescription pain drugs and common over-the-counter medications made at a Novartis manufacturing plant.

The issue stems from manufacturing problems at a Lincoln, Neb., facility that triggered a recall Sunday of 1,645 lots of Novartis' over-the-counter drugs, including Excedrin, Bufferin, NoDoz and Gas-X.

The company has received hundreds of complaints of broken and chipped pills and inconsistent bottle packaging that could cause pills to be mixed up.

Consumers are advised to stop using the products and contact the company for a refund.

FDA officials warned Monday that some of Novartis' over-the-counter pills may have accidentally been packaged with powerful prescription painkillers made at the same facility.

The opioid drugs are sold by Endo Pharmaceuticals as Percocet, Endocet, Opana and Zydone.

Several St. Louis-area grocery and pharmacy chains sell Novartis products as store brands. However, a spokesperson for Novartis says the recall affects only brand name products. It does not affect store brands made by Novartis and sold under the names of grocers and pharmacies.

Endo Pharmaceuticals Holdings Inc. of Chadds Ford, Pa., said it was not aware of any confirmed product mix-ups that had reached patients or caused any injuries. A spokeswoman for Novartis said late Monday that only Gas-X was produced on the same manufacturing line as the opioid drugs.

FDA officials say they are not recalling the painkillers because they are essential medications for many patients and the risks of stray pills are low.

Harry Jackson Jr. of the Post-Dispatch contributed to this report.