WASHINGTON (AP) - A potent muscle relaxant used in hospitals was pulled off the market after its maker learned of five deaths linked to the drug, called Raplon.

The voluntary withdrawal by manufacturer Organon Inc. makes Raplon the 12th drug pulled off the market since 1997.

Surgeons inject Raplon before inserting breathing tubes into patients' throats. It typically was used for short surgical procedures because it wears off quickly.

The FDA warned when it approved Raplon about a rare side effect - an airway spasm blocking normal breathing. Clinical studies suggested these bronchospasms, which can range from mild to severe, occurred in 3.2 percent of patients, but all were successfully treated. Still, the FDA strongly warned that Raplon should be used only by experienced physicians with resuscitation equipment on hand.

Manufacturer Organon Inc. began writing hospitals this week that it was stopping sales, after learning of five deaths over about nine months.

Surgeons can use other muscle relaxants, but similar medications carry a bronchospasm risk, too. The difference is that competing drugs seem to cause milder bronchospasm cases, said FDA's Dr. John Jenkins, which agreed with Organon's decision to withdraw Raplon after investigating the new death reports.

The recent spate of drugs withdrawn from the market has some critics questioning if the FDA, under congressional pressure to speed drug approvals, reviews drugs so quickly that it misses dangers.

However, the FDA said Thursday it had spent more than a year reviewing Raplon before approving it in 1999. Drugs often are studied in too few people for rare problems to show up until they're used in tens of thousands of patients. Also, risks can arise when doctors don't heed a drug's warnings or use it in the wrong kind of patient.

It's not clear what happened with Raplon, Jenkins said, although some of the deaths occurred in people with a history of breathing problems.

Copyright 2001 The Associated Press. All rights reserved.