A drug tested on a few thousand people for a few months cannot be assumed to be safe for millions of people to use over the years to come, said Rep. Edward Markey.

Markey said that of 91 post-marketing studies required by the FDA, 42 have not been completed and half of those have not even been started.

Drugs designed for people with life-threatening illnesses can sometimes receive expedited approval to make them available more quickly.

In those cases the companies are required to do a follow-up study of the people who use the drug to check for effectiveness and any side effects that may not have been seen in earlier, smaller studies.

'Dragging Their Feet'

"It is outrageous that drug companies and the FDA have been dragging their feet when it comes to conducting required post-marketing studies," Markey said in a statement.

A drug tested on a few thousand people for a few months cannot be assumed to be safe for millions of people to use over the years to come, Markey said.

He also said a staff analysis of the work indicated that many companies also have not disclosed information regarding postmarketing studies to their investors.

'Failures of the Drug Companies and the FDA'

Markey said he plans to introduce a bill "to address the failures of the drug companies and the FDA to do their due diligence."

FDA spokeswoman Suzanne Trevino said the agency has not yet seen the report.

Spokesman Jeff Trewhitt of the trade group Pharmaceutical Research and Manufacturers of America said that while the group has not had a chance to review Markey's report, "we believe the regulatory program at FDA works well."