Medicare Part D plans vary, but most appear to cover common medications at low co-payments

June 19, 2007

An examination of Medicare Part D plans in California and Hawaii reveals wide variations in drug formularies, but indicates that for many classes of drugs, it is possible to find at least one or more drug that is covered by nearly all Part D plans, according to a study in the June 20 issue of JAMA.

Nearly 23 million of the 43.9 million eligible Medicare beneficiaries have enrolled in the Medicare Part D prescription drug benefit, according to background information in the article. Because of the number and variety of plans, clinicians often find it difficult to know which drugs are covered by Part D plan formularies. Previous studies indicate that two-thirds of clinicians say they lack familiarity with Part D formularies, and three-fourths have been asked by pharmacies or patients to change a prescription to a different drug so that it would be covered by the patient's plan. The number of Part D plans is increasing, with 1,875 stand-alone prescription drug plans in 2007 compared with 1,429 in 2006. Many states have more than 50 Part D plans. "Wide formulary variation can lead clinicians to inadvertently prescribe drugs that are not covered by insurance or that require a high co-payment, increasing patients' financial burden and decreasing medication adherence," the authors write.

Chien-Wen Tseng, M.D., M.P.H., of the John A. Burns School of Medicine at the University of Hawaii, Honolulu, and colleagues conducted a study to determine whether Part D formularies in California (the state with the most Medicare beneficiaries) and Hawaii have at least one drug within each of eight treatment classes for hypertension, hyperlipidemia, and depression that can be identified for clinicians as "widely-covered" by the vast majority of Part D plans. The researchers used the Web site, from March 1-April 15, 2006, to examine 72 California and 43 Hawaii Part D formularies' coverage of eight treatment classes (angiotensin-converting enzyme [ACE] inhibitors, angiotensin II receptor blockers [ARBs], beta-blockers, calcium channel blockers, loop diuretics, selective serotonin reuptake inhibitors, statins, and thiazide diuretics), with evaluation of how often drugs were widely covered (here defined as inclusion in 90 percent or more of formularies at co-payments of $35 or less without prior authorization).

In an analyses of 72 formularies, the researchers found that coverage for 75 specific drugs ranged from 7 percent to 100 percent of formularies and averaged 69 percent across all drugs. Formulary coverage (percentage of formularies covering each drug, averaged across all drugs within a class) was highest for thiazide diuretics (90 percent) and beta-blockers (85 percent), followed by selective serotonin reuptake inhibitors (69 percent), calcium channel blockers (66 percent), ACE inhibitors (66 percent), statins (49 percent), and ARBs (39 percent).

Overall, less than half of drugs (45 percent) were widely-covered. However, 7 of 8 treatment classes (excluding ARBs) had at least one widely covered drug. Nearly all widely-covered drugs (94 percent) were generic drugs, and three-fourths of generic drugs (73 percent) were widely-covered. On average, generic drugs were covered by 90 percent of formularies. Six percent of brand-name drugs were widely- covered. Adopting the stricter requirement of coverage to include 95 percent or more of formularies at co-payments of $15 or less did not change the study findings that 7 of 8 treatment classes had at least one widely-covered drug.

"In this study to evaluate Medicare Part D plan formulary variation, the coverage of individual drugs varied extensively, indicating the potential difficulties that clinicians can face in knowing which drugs are covered or are more affordable," the authors write. "... a potential way to address formulary variation would be to identify, within a class, which drugs are widely covered and generally more affordable for clinicians to consider. This could substantially reduce clinicians' administrative burden from formulary variation and lower the risk that Medicare beneficiaries are inadvertently prescribed noncovered or higher cost-sharing drugs."

"Clinicians should also be alerted to those classes with no widely covered drugs, from which they should not prescribe without first checking formulary coverage. For example, the maximum coverage for any single ARB was 81 percent of formularies. If this type of coverage information were made available in interactive fashion via a Web site, personal digital assistant-based tool, or e-prescribing software, clinicians could use this knowledge in the clinical encounter during collaborative decision making on selecting medications."

(JAMA. 2007;297:2596-2602. Available pre-embargo to the media at

Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
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