The U.S. Food and Drug Administration warned health care workers on Wednesday to be careful when using two similarly named but very different drugs, saying a recent mix-up involving the two medications had injured a patient.

The agency said the incident occurred when a pharmacist confused Durasal, a wart remover not approved by the FDA, with Durezol, an FDA-approved steroidal eyedrop used to treat inflammation and pain following eye surgery.

The agency said the mix-up -- the latest in a series of cases involving confusion between the two drugs -- had caused "serious injury" to the patient.

Normally, the FDA said it screens proprietary names as part of the drug approval process to avoid any confusion with products already on the market. But because the wart remover was an unapproved product, its name was not vetted by the agency.

The FDA said that Elorac Inc, the Vernon Hills, Illinois-based distributor of the Durasal, had not responded to a request from the agency that it remove the product from the market place and has not recalled the product despite the FDA's concern about the risk it poses to patients.

Jeffrey Bernstein, a spokesman for Elorac, did not immediately return a message requesting comment on the FDA's warning.