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Health Services Research & Development

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2005 HSR&D National Meeting Abstract

3023 — Prescribing Generic or “Preferred” Medications Improves Adherence in Three-Tier Pharmacy Plans

Author List:
Shrank WH (West LA Veterans Affairs Healthcare System)
Hoang T
Ettner SL
Glassman P
Nair K
London R
DeLapp D

A majority of Americans with prescription drug coverage are enrolled in three-tier pharmacy benefit systems and the VA Healthcare system has considered adopting such a system. These plans offer substantial choice in prescribing, and assess graded copayments to steer patients towards “preferred” formulary drugs. We study whether prescriptions for generic or preferred branded agents, when initiating chronic therapy, influences the likelihood that patients will be adherent to treatment regimens as compared to initial prescriptions for non-preferred medications.

We analyzed pharmacy claims from patients enrolled in three-tier plans in a large Western health plan. Adherence was evaluated in six classes of chronic medications: statins, calcium channel blockers, oral contraceptives, orally inhaled steroids, angiotensin receptor blockers and ACE-Inhibitors. Adherence was measured using the proportion of days covered (PDC) in each drug class during the first year of therapy. We evaluated the influence of the formulary status of the initial prescription in a drug class on PDC and “good” adherence (PDC >80%).

6075 patients in the health plan filled a new prescription in one of the classes evaluated, 1495 (25%) for non-preferred, (greatest co-pay) branded medications, 3485 (57%) for preferred (middle co-pay) branded drugs and 1097 (18%) for generic drugs (lowest co-pay). After controlling for patient age, gender, income and medication utilization, PDC was 9.49% greater for patients who filled prescriptions for generic medications (p<.0001) than for patients who received non-preferred branded medications. PDC was 5.74% greater for patients that filled prescriptions for preferred branded medications (p<.0001) than for patients who filled non-preferred prescriptions. Patients who received generic medications were almost twice as likely (OR 1.94, p<.0001) to achieve “good” adherence, and patients who received “preferred” branded medications were more than one third more likely (OR = 1.36, p<.0001) to achieve “good” adherence, than those who received non-preferred, branded medications.

When initiating chronic therapy in three-tier pharmacy benefit plans, identifying the medication within a class that requires the lowest copayment can have a significant impact on that patient’s adherence to the prescribed medication.

Prior to developing a tiered pharmacy benefit system for veterans, care must be taken to create systems that will help steer patients towards medications that comply with patients’ formularies and minimize out-of-pocket costs.

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