 Prior authorization helps ensure that patients receive correct medications.Step therapy is a process in which a plan requires an individual to try, and prove ineffective, one or more specified lower-cost drugs before a higher-cost drug in the same therapeutic class is approved.A 2008 study found that the % of Medicare beneficiaries who reported forgoing medications due to cost dropped with Part D, from 15.2% in 2004 and 14.1% in 2005 to 11.5% in 2006.