Updated

Democratic Sen. Bill Nelson of Florida is urging the inspector general of the Department of Health and Human Services to investigate reports that prescription drug makers are raising prices ahead of Congress' sweeping health care reform bill.

In a letter sent to Health inspector Daniel R. Levinson on Wednesday, Nelson said he is proposing an amendment that would force the country's biggest pharmaceutical companies to offset more of the costs.

Nelson cited a recent AARP study that found that drugmakers have dramatically upped the cost on commonly used brand-name drugs.

"I want to know if there's a back-door move under way by the drugmakers to recover some of the concessions they've promised for health care reform," Nelson said.

The analysis by AARP's Public Policy Institute released Monday found that the price of many prescription drugs used by Medicare beneficiaries rose by 9.3 percent from October 2008 to September 2009 -- a rate that's higher than usual when compared to previous years.

The study reported that prices increased for 96 percent of brand-name drugs over the last year -- despite a negative general inflation rate.

"This report confirms what most older Americans already know: drugmakers are raising their prices and enjoying windfall profits, even as the rest of the economy is suffering," AARP Executive Vice President John Rother said in a press release Monday.

"The pharmaceutical industry should be embarrassed when it sees its own price increases put side by side with the general inflation rate. Even as the cost of most goods and services drops, a person taking just one brand-name drug now pays $200 more per year than a year ago," said Rother.

Nelson called the increase "troubling" and is pressing Levinson to fully investigate AARP's findings.

"As you know, President Obama reached an agreement with the Pharmaceutical Research and Manufacturers of America, which pledged $80 billion in support of health reform efforts," Nelson wrote in his letter to Levinson.

"A significant portion of this support was in the form of rebates to the Medicaid program and discounts offered to seniors in the Medicare Part D coverage gap," he wrote.