BACKGROUND: Despite the proven efficacy of prescription regimens in reducing disease symptoms and preventing or minimizing complications, poor medication adherence remains a significant public health problem. Medicare beneficiaries have high rates of chronic illness and prescription medication use, making this population particularly vulnerable to non-adherence. Failure to fill prescribed medication is a key component of nonadherence. OBJECTIVES: To (1) determine the rates of self-reported failure to fill at least 1 prescription among a sample of Medicare beneficiaries in 2004, (2) identify the reasons for not filling prescribed medication, (3) examine the characteristics of Medicare beneficiaries who failed to fill their prescription (s), and (4) identify the types of medications that were not obtained. METHODS: The study is a secondary analysis of the 2004 Medicare Current Beneficiary Survey (MCBS), an ongoing national panel survey conducted by the Centers for Medicare & Medicaid Services (CMS). Medicare beneficiaries living in the community (N =14,464) were asked: "During the current year [2004], were there any medicines prescribed for you that you did not get (please include refills of earlier prescriptions as well as prescriptions that were written or phoned in by a doctor)?" Those who responded "yes" to this question (n=664) were asked to identify the specific medication(s) not obtained. Rates of failure to fill were compared by demographic and income categories and for respondents with versus without self-reported chronic conditions, identified by asking respondents if they had ever been told by a doctor that they had the condition. Weighted population estimates for nonadherence were calculated using Professional Software for SUrvey DAta ANalysis for Multi-stage Sample Designs (SUDAAN) to account for the MCBS multistage stratified cluster sampling process. Unweighted counts of the prescriptions not filled by therapeutic class were calculated using Statistical Analysis Software (SAS). RESULTS: In 2004, an estimated 1.6 million Medicare beneficiaries (4.4%) failed to fill or refill 1 or more prescriptions. The most common reasons cited for failure to fill were: "thought it would cost too much" (55.5%), followed by "medicine not covered by insurance" (20.2%), "didn't think medicine was necessary for the condition" (18.0%), and "was afraid of medicine reactions/contraindications" (11.8%). Rates of failure to fill were significantly higher among Medicare beneficiaries aged 18 to 64 years eligible through Social Security Disability Insurance (10.4%) than among beneficiaries aged 65 years or older (3.3%, P< 0.001). Rates were slightly higher for women than for men (5.0 vs. 3.6%, P= 0.001), for nonwhite than for white respondents (5.5% vs. 4.2%, P=0.010), and for dually eligible Medicaid beneficiaries than for those who did not have Medicaid coverage (6.3% vs. 4.0% P=0.001). Failure-to-fill rates were significantly higher among beneficiaries with psychiatric conditions (8.0%, P<0.001); arthritis (5.2%, P<0.001); cardiovascular disease (5.2%, P=0.003); and emphysema, asthma, or chronic obstructive pulmonary disease (6.6%, P<0.001) than among respondents who did not report those conditions, and the rate for respondents who reported no chronic conditions was 2.5%. Rates were higher for those with more self-reported chronic conditions (3.2%, 4.0%, 4.3%, and 5.9% for those with 1, 2, 3, and 4 or more conditions, respectively, P< 0.001). Among the prescriptions not filled (993 prescriptions indentified by 664 respondents), central nervous system agents, including nonsteroidal anti-inflammatory drugs, were most frequently identified (23.6%, n = 234), followed by cardiovascular agents (18.3%, n =182) and endocrine/metabolic agents (6.5%, n = 65). Of the reported unfilled prescriptions, 8.1% were for antihyperlipidemic agents, 5.4% were for antidepressant drugs, 4.6% were for antibiotics, and 29.9% were for unidentified therapy classes. CONCLUSION: Most Medicare beneficiaries fill their prescriptions, but some subpopulations are at significantly higher risk for nonadherence associated with unfilled prescriptions, including working-age beneficiaries, dual-eligible beneficiaries, and beneficiaries with multiple chronic conditions. Self-reported unfilled prescriptions included critical medications for treatment of acute and chronic disease, including antihyperlipidemic agents, antidepressants, and antibiotics.
