This supplement was written by William T. Elliott, MD, FACP, Chair, Formulary Committee, Kaiser Permanente, California Division; Assistant Clinical Professor of Medicine, University of California-San Francisco. In order to reveal any potential bias in this publication, we disclose that Dr. Elliott reports no consultant, stockholder, speaker’s bureau, research, or other financial relationships with companies having ties to this field of study. For questions and comments, please e-mail:

Medication nonadherence is widespread among patients, according to a new study from Canada. In a cohort of nearly 16,000 patients in a primary care network, primary adherence (defined by not filling a prescription) was monitored between 2006 and 2009. Overall, 31.3% of more than 37,000 prescriptions were not filled within 9 months. The most expensive drugs were the least likely to be filled (odds ratio, 1.11; 95% confidence interval [CI], 1.07 to 1.17) as were topicals, gastrointestinal drugs, and autonomic drugs compared with anti-infectives. Older patients were more likely to fill their medications as were patients with no prescription copay. Patients who saw their primary care physician more frequently were also more likely to fill their prescription. The authors conclude that primary nonadherence is common (as much as one-third of prescriptions) and may be improved by lower drug costs and lower copayments as well as close follow-up (Ann Intern Med 2014;160:441-450).