The US Food and Drug Administration has revealed in its annual report for 2005 that two thirds of the 1,231 post-marketing studies that pharmaceutical companies had committed to as a condition of product approval had not started by September 30.

At present, the FDA has no authority in law to force companies to complete post-marketing studies, also known as Phase IV trials, but a bill that would give it this power has been introduced in the US Congress by Senators Chuck Grassley and Christopher Dodd.

Last month, the FDA started a consultation procedure to get advice on how it could encourage pharmaceutical firms to fulfil these obligations promptly.

The FDA report defined just 28 studies (2%) as delayed, and 797 (65%) as pending. 231 (19%) were already ongoing, and three (less than 1%) had been terminated. Only 172 (14%) had been submitted to the agency by the time the report was drawn up, according to the FDA.

John Jenkins, director of the FDA's Office of New Drugs said the percentages were in line with findings from previous years.

In response to the report, the Pharmaceutical Research and Manufacturers of America issued a statement noting that 'pending' does not necessarily mean delayed, but rather means that the tasks of developing research protocols, finding investigators and researchers, and even of recruiting patients to participate in the study is in process.

Jenkins agreed that just because many of the studies have not begun as yet, it does not mean they will never be started, noting that 116 of the 797 pending studies were committed to during the 12 months ending in September. The clinical trials can take six months to a year to design and launch, he noted.