The HHS Office of Inspector General (OIG) has released a report entitled "Review of Additional Rebates for Brand-Name Drugs With Multiple Versions.” The OIG found that of the top 150 brand-name drugs for calendar year 2007 ranked by Medicaid reimbursement, 114 had more than one version. For 65 of the 114, the prices of the earliest versions of the drugs exceeded their inflation-adjusted prices when the new versions entered the market. The OIG calculated that for 1993 through 2007, states could have collected approximately $2.5 billion in additional rebates for these 65 drugs if the baseline average manufacturer prices (AMP) of the new versions had been reduced to reflect price increases in excess of inflation for the earliest versions, since federal law requires manufacturers to pay an additional rebate when the AMP for a brand-name drug increases more than inflation. The OIG cautions that it "did not evaluate the drug manufacturers’ bases for developing the new versions of existing drugs," but because rebates are calculated separately for each version of a drug, "manufacturers could develop new versions of existing brand-name drugs solely to avoid paying additional rebates when they substantially increase prices." The OIG concludes that "[w]ithout some modification to the rebate law, the risk of manufacturers taking advantage of this potential loophole may increase over time." The OIG recommended that CMS continue to seek legislative authority to modify the rebate formula calculation to ensure that manufacturers cannot circumvent paying additional rebates by bringing new versions of existing brand-name drugs to market. CMS concurred with the OIG’s findings and recommendation.