Identifying Widely Covered Drugs and Drug Coverage Variation Among Medicare Part D Formularies

Researchers examined the extent of coverage for an array of treatment classes of prescription drugs by formularies that were part of Medicare Part D prescription drug benefits. Information gleaned from the Medicare Web site yielded 4,147 occurrences of coverage for 75 drugs in eight treatment classes from 72 formularies in California. Formularies in Hawa

Key Findings:

  • For the 75 drugs examined in the study, coverage was seen in 7 percent to 100 percent of formularies with an average coverage rate of 69 percent.
  • Thiazide diuretics (90%) had the highest rate of formulary coverage for the drug treatment classes while angiotension II receptor blockers, or ARBs, had the lowest rate at 39 percent.
  • Even drug classes with the most frequent coverage were found to have at least one drug not covered by two-thirds of formularies.
  • Fewer than half of the 75 drugs analyzed in the study saw wide coverage or coverage by 85–95 percent of formularies. Of the eight treatment classes studied, all but one (ARB) contained at least one drug that was widely covered.
  • When the coverage rate was set at 95 percent or higher and co-payment rates were set at $15 or below, seven of eight treatment classes still had at least one drug that was widely covered by formularies.
  • Generic drugs accounted for 73 percent of widely covered drugs with brand-name drugs comprising only 6 percent of widely covered drugs. One-third of formularies covered brand-name-only drugs and 90 percent covered generic drugs.