Counterfeit prescription drugs and illegal distribution schemes could threaten the health and safety of American consumers, a congressional report said yesterday.

"American consumers cannot purchase prescription drugs with the certainty that the products are safe and effective," said Stephen F. Sims, a principal author of the report who is staff attorney for the House Energy and Commerce subcommittee on oversight and investigations.

The 30-page report documented instances of fake drugs sold on the open market and elaborate illegal or quasilegal marketing schemes known as drug diversion.

Diverted merchandise is generally any brand-name product that is not obtained directly from the manufacturer or authorized dealer.

Because of complex, multimillion-dollar diversion operations, enforcement by government agencies and legitimate manufacturers is seriously undermined, said panel chairman Rep. John D. Dingell (D-Mich.).

A major case last fall involving counterfeit Ovulen 21, a birth-control pill, prompted the subcommittee's inquiry. Nearly 2 million bogus pills were imported from Panama. They were acquired by American Medic Sales Inc. of North Miami, and then sold to a California laboratory.

Within a week, the pills landed on the shelves of Harry's Pharmacy in Palos Heights, Ill., where about 1,275 packages were apparently sold, the report said.

In all, the counterfeit pills were sold in 18 states before the Food and Drug Administration seized them.

Sims said a survey of drug companies indicated there had been little domestic counterfeiting of brand-name drugs in the past five years, but fake-drug manufacturing abroad is apparently widespread.

In response to questions, Sims also said U.S. Customs Service and FDA agents are often overworked, particularly at port cities in Florida where drugs might enter.

FDA spokesman Don McLearn said he could not comment on the report because he had not seen it, but that in the case of the Ovulen 21 pills, the agency acted quickly to recall the fake pills.