Increasing pharmaceutical copayments: impact on asthma medication utilization and outcomes.

OBJECTIVES: Unintended consequences may result from changes in pharmacy benefit design. The objective was to determine the impact of increasing patient prescription copayments for guideline recommended, long-term asthma controller (LTC) medications on asthma-related medication use and healthcare services. STUDY
DESIGN: We used 2005 MarketScan healthcare and pharmacy claims data to identify asthma (International Classification of Diseases, 9th Revision, Clinical Modification [ICD-9-CM] diagnosis code 493.xx) patients aged 12 to 64 years who were continuously enrolled through 2006 with ≥ 1 claim for an asthma medication in 2005. LTCs included: inhaled corticosteroid (ICS) (n = 10,251), ICS plus long-acting beta agonist (COMBO) (n =27,407), and leukotriene receptor antagonist (LTRA) (n = 20,664).
METHODS: Using multivariable models, we estimated the associations between changes in LTC copayments and LTC consumption and asthma-related outpatient and emergency department (ED) visits.
RESULTS: Patients were dichotomized into ≥ $5 average increase in patient copayments per month of medication supplied (yes/no). The mean annual change (2005-2006) in copayments per month was $13.23 versus -$3.88 (ICS), $11.76 versus -$3.06 (COMBO), and $9.78 versus -$2.06 (LTRA). The ≥ $5 group experienced a significant decline in average annual days of medication supplied of -47.1 days of ICS (95% CI -43.5 to -50.8), -35.3 days of COMBO (-32.4 to -38.2), and -47.5 days of LTRA (-43.2 to -51.7). Among COMBO and LTRA medication users, the ≥ $5 copayment increase was associated with more asthma-related outpatient visits and ED visits compared with the < $5 group.
CONCLUSIONS: The findings suggest that even small changes in average copayment for asthma medications can result in significant reductions in medication use and unintended increases in healthcare services.