OBJECTIVES: To study primary nonadherence to medications prescribed in primary care, defined as failure to dispense a new medication or its equivalent within six months of the prescription issue date.

METHODS: We applied a novel data linkage between prescribing data from primary care electronic medical records with comprehensive pharmacy dispensing claims between January 2013 and April 2019 in British Columbia (BC) to estimate primary medication nonadherence and its predictors. We used hierarchical multivariable logistic regression to determine prescriber, patient and medication factors associated with primary medication nonadherence among community-dwelling patients in primary care.

RESULTS: Among 150,565 new prescriptions to 34,243 patients, 17% of prescriptions were never filled. Primary medication nonadherence was highest for drugs prescribed mostly on an as-needed basis, including topical corticosteroids (35.1%) and antihistamines (23.4%). In multivariable analysis, primary medication nonadherence was lower for prescriptions issued by male prescribers (OR 0.66, 95% CI 0.50 to 0.88). Primary medication nonadherence decreased with patient age (OR 0.91, 95% CI 0.90 to 0.92 for each additional 10 years), but increased with polypharmacy among patients 65 or older. Patients filled over 82% of their medication prescriptions within two weeks after their primary care provider visit.

CONCLUSIONS: Prevalence of primary medication nonadherence to new prescriptions was 17%. Interventions to address primary medication nonadherence may want to target older patients with multiple medication use and within the first two weeks of the prescription issue date.