Philadelphia's Lannett Co. Inc. won a reprieve late Thursday from a federal-government order demanding that the generic drug-maker immediately stop selling an unapproved version of liquid morphine.

The U.S. Food and Drug Administration said it reconsidered after health-care professionals and families complained that the decision would make it more difficult to relieve pain for some dying patients.

Lannett chief executive Arthur Bedrosian said today that he was "grateful that the agency reacted quickly." The company will give the FDA evidence next week that its drugs have long been considered safe and effective, he said.

"I want to be clear that Lannett doesn't sell anything illegally," Bedrosian said.

Cynthia Reilly, director of the practice-development division for the American Society of Health-System Pharmacists, said the type of liquid morphine involved was especially useful with patients who had trouble swallowing because it is concentrated, allowing fewer doses.

But the FDA emphasized in its letter to Lannett and other companies that it was not backing off its broader effort to get unapproved drugs off the market. Many drugs came on the market before the FDA even existed.

"FDA intends to continue to take aggressive enforcement action against marketed unapproved drugs," the agency's letter said.

On March 30, the FDA told Lannett, its subsidiary Cody Labs, and 12 other companies to stop selling the drugs within 60 days. On Thursday, the agency said it was extending that period to 180 days "after any firm receives approval for a morphine sulfate oral solution 20 mg/ml product."

The extension does not apply to another Lannett product the FDA had cited in its March 30 letter, Hydromorphone HCI Tablets.

Contact staff writer Miriam Hill at 215-854-5520 or hillmb@phillynews.com.