Nearly a third of patients fail to fill first-time prescriptions, which may be important in determining clinical outcomes, according to an article published in Annals of Internal Medicine.

Many chronic illnesses can be successfully managed with pharmaceutical interventions, but nonadherence to prescribed medications is an issue. Researchers studied 15,961 patients in a primary care network of 131 physicians to estimate the incidence of primary nonadherence (failure to fill a first-time prescription) and association of drug, patient, and physician with nonadherence. The researchers found nearly one third of all initial drug prescriptions were not filled within 9 months. Nonadherence was highest for expensive drugs and chronic preventive therapies for conditions such as ischemic heart disease and depression.

Prescriptions for antibiotics were most likely to be filled. Patients with higher copayments, recent hospitalization, and more severe comorbid conditions were at greater risk for nonadherence. Patients that had more visits with the prescribing physician were more likely to fill their prescriptions. The authors suggest that lower copayments and greater follow-up care with prescribing physicians may reduce the risk for nonadherence.