BACKGROUND:

Between the promise of evidence-based medicine and the reality of inadequate patient outcomes lies patient adherence. Studies of prescription adherence have been hampered by methodologic problems. Most rely on patient self-report of adherence or cross-sectional data of plan-wide prescription fills to estimate patient-level adherence.

METHODS:

We conducted a retrospective cohort study and linked individual patient data for incident prescriptions for antihypertensive medications from electronic health records (EHRs) to claims data obtained from the patient's insurance plan. Clinical data were obtained from the Geisinger Clinic, a 41 site group practice serving central and northeastern Pennsylvania with an EHR in use since 2001. Adherence was defined as a prescription claim generated for the first-fill prescription within 30 days of the prescribing date.

RESULTS:

Of the 3,240 patients written a new, first-time prescription for an antihypertensive medication, 2,685 (83%) generated a corresponding claim within 30 days. Sex, age, therapeutic class, number of other medications prescribed within 10 days of the antihypertensive prescription, number of refills, co-pay, comorbidity score, baseline blood pressure (BP), and change in BP were significantly associated with first-fill rates (P < 0.05).

CONCLUSIONS:

Patients who are older, female, have multiple comorbidities, and/or have relatively lower BPs may be less likely to fill a first prescription for antihypertensive medications and may be potential candidates for interventions to improve adherence to first-fill prescriptions.