The FDA will often approve a drug on the condition that its maker perform a study after the drug is on the market.  The trouble is that many pharmaceuticals ignore their obligation to run those studies:

In a report released Monday, the Government Accountability Office said that from 1992 through Nov. 20, 2008, the food and drug agency asked drug makers to complete 144 studies associated with 90 drug applications, and that drug makers had completed just two-thirds of the requested studies. Fifteen of the 52 uncompleted studies have been pending for more than five years, and several have been pending for more than eight years, the report said.

Source: Industry Years Behind on Testing Approved Drugs –

How about a system of modest fines? Say, $1,000 per day after a study is say, three months late.  Some of those studies have been pending for more than eight years.  That would work out to a fine of around $3 million dollars.  In the scheme of things, it’s not a very large fine for a pharmaceutical company to pay, but (a) they would add up, and (b) the FDA could use the funds.