The wholesale prices of brand name medicines most commonly prescribed to elderly Americans increased an average of 7.4 percent last year, an increase about 2.5 times greater than general inflation, says a study released Wednesday by the advocacy group AARP.

The study looked at 220 brand name prescription drugs and found that all but four had wholesale price increases in 2007, the Associated Press reported. Among the top 25 medicines, the sleep aid Ambien had the largest price increase (27.7 percent). At the other end of the list were the blood thinner Plavix (0.5 percent increase) and the cholesterol drug Zocor (no increase).

The increase in drug prices in 2007 continues a long-standing trend, said AARP, which noted that price increases have been slightly larger since the Medicare drug benefit took effect Jan. 1, 2006, the AP reported. In the four years before the drug benefit was launched, wholesale drug prices increased between 5.3 percent and 6.6 percent a year, according to AARP figures.

There were loud complaints about high drug prices at the time that Congress approved the Medicare drug benefit, but that outrage has since eased, perhaps because the federal government now pays for much of the cost of Medicare beneficiaries’ drugs, the news service said.

“Unfortunately, many manufacturers have taken the absence of an outcry as a green light to go ahead and raise prices even more,” said John Rother, AARP’s policy director, the AP reported.