Four Republican Senators have written a letter to their party leaders saying they intend to block a recently passed Senate spending bill because the legislation contains a provision that would ban pay-for-delay deals between brand-name and generic drugmakers.

The inclusion of the amendment in appropriations legislation “is a gross breach of Senate custom,” because the Judiciary Committee considered similar legislation last October, according to the letter to Senate GOP leaders written by Tom Coburn of Oklahoma, John Cornyn of Texas, South Dakota’s John Thune and Jeff Sessions of Alabama. “We believe that the reported bill gives excessive power over such settlements to the FTC and that the bill would do serious violence to the Hatch-Waxman process for the market entry of generic drugs” (Here is the letter).

The Senate Appropriations Committee approved the spending bill two months ago but all of the Republicans voted against the measure (back story). A companion House bill was recently passed as part of the Supplemental Appropriations Act of 2010, although this measure does not call for a ban, but instead allows the US Federal Trade Commission to act on any deal believed to be illegal. This approach also gives drugmakers a chance to prove otherwise.

The move comes as FTC commish Jon Leibowitz has been working hard to convince Congress to pass a law that would limit these deals, which the agency is fighting in the courts, but with only mixed success (see this). The FTC has called the settlements anti-competitive, and the Congressional Budget Office has estimated the House bill would save the federal government $2.6 billion over 10 years by reducing drug costs. This story was first reported in Congress Daily.