Between 1998 and 2008, 75% of new drugs approved in the United States and the European Union, as well as 50% of those approved in Japan, had post-marketing study commitments attached to them, a recent analysis by the Tufts Center for the Study of Drug Development found.

For those new drugs that do require post-marketing or Phase IV studies, the average number of studies per drug ranges from 10.8 in the EU to 8.9 in the US and 1.7 in Japan, notes the analysis published in the July/August Tufts CSDD Impact Report. The number of required studies also varies by therapeutic area.

When they are a condition of drug approval, post-marketing commitments in the EU and Japan are more likely to arise from safety concerns than in the US, the Tufts Center said. Phase IV studies may be designed to generate data on a product’s safety and efficacy, its prescribing and use, or the consistency of the manufacturing process.

“What used to be the exception is increasingly becoming the rule for new drug approvals,” commented Christopher-Paul Milne, associate director at the Tuft’s Center and the study’s author.

While post-approval studies may push up the cost of marketing new medicines, they may also “offer a silver lining in that potential safety issues are identified earlier and the increased knowledge of a drug’s safety and efficacy allows drug sponsors to serve patient populations better”, Milne pointed out.

In a survey published by the Tufts CSDD in May 2007, 68% of clinical study sponsors and 79% of non-clinical study sponsors told the Center's researchers that post-marketing study results had contributed either marginally or not at all to their understanding of the safety, efficacy or quality of their new products. However, 32% of the respondents felt the studies had “significantly or very significantly” increased their understanding.