Pharmacologic therapy initiation, compliance and continuation are important components of disease management. 1 Medication nonadherence is a complex, multidimensional and multifaceted problem that contributes to suboptimal health outcomes and poses substantial challenges and financial burdens on the health care system. [2][3][4][5][6] It is estimated that as much as 50% of patients worldwide do not take their medications as pre scribed. 7 Although the causes are well understood, improving medication adherence has proven difficult. 8 Primary and second ary nonadherence are separate subsets of medication nonadherence. Unlike secondary nonadherence -which occurs when patients fill or refill the prescription but do not use it as prescribed -in primary nonadherence, patients do not fill the initial prescription or an appropriate alternative within a clinic ally acceptable time period. 9,10 Most studies of medication nonadherence that rely on claims data for dispensed prescriptions measure secondary adherence, persistence or discontinuation to pharmacother apy, but fail to account for medication initiation. 10 Research examining primary nonadherence is limited, 11 with most studies relying on selfreported measures of nonadherence to incident prescriptions via surveys, 12,13 which are hampered by methodologic limitations such as small sample sizes and self reporting bias. 14 Other studies rely on electronic prescriptions of patients discharged from hospital, 5,15,16 which constitute a subsample of patients with higher comorbidities and a distinct, shortlived patient-clinician relationship. Relatively recent shifts from paper prescriptions to electronic systems make studying primary nonadherence more feasible on larger and more rep resentative samples. 17