Higher out-of-pocket costs for buprenorphine increase early stage OUD treatment dropout
Background: More than half of new patients started on buprenorphine-naloxone (BN) treatment for opioid use disorder (OUD) discontinue prematurely [1-2], elevating the risk of relapse, overdose, morbidity and mortality . The dropout rate is highest in the first few weeks of treatment [4-5]. Whether patients' out-of-pocket costs for BN affect early dropout is unknown. We investigated the impact of out-of-pocket costs on early dropout among new patients in office-based treatment settings.
Methods: This is a retrospective cohort study using data from a nationwide commercial healthcare claims repository in the United States. Patient selection criteria were (1) age 18 years or older, (2) continuous insurance coverage from 1/1/2018 through 6/30/2019, (3) an OUD diagnosis, (4) a BN prescription fill in the first quarter 2019, and (5) no methadone or BN fills in 2018. Our exposure variable was out-of-pocket costs (copay and deductible) for the first BN fill, dichotomized at the median. Our outcome of interest was BN treatment discontinuation at 5 weeks (y,n). Time to discontinuation was measured by days supplied of BN medication summed across all prescription fills. We used propensity score analysis to estimate the average treatment effect (ATE) of high vs. low out-of-pocket BN costs on treatment dropout at 5 weeks. Propensity scores were computed using the potential confounds of age, sex, race/ethnicity, education, income, geographic region, BN strength, type of medical insurance plan, and indicators of adverse selection (health status measured by Charlson comorbidity score and health care services utilization measured by number of office visits in 2018). We evaluated whether the propensity score assumptions of covariate balance and positivity were met.
Results: A cohort of 533 privately insured patients (median age = 51 years, sd = 16; 56% female) was followed for 13 weeks from the date of the first BN fill. The median out-of-pocket costs for the first fill was $35 (IQR = $62). Adjusting for propensity scores, 28% of individuals with high out-of-pocket costs discontinued treatment in the first 5 weeks vs. 20% with low out-of-pocket costs. The ATE was -0.08 (95% CI: -0.15 to -0.01, P = 0.037). Violations of the covariate balance and positivity assumptions were not detected. The difference between the exposure groups was supported in sensitivity analyses.
Conclusions: Among privately insured patients initiating BN treatment for OUD in outpatient settings, higher out-of-pocket prescription costs increased the likelihood of early treatment dropout. Lowering costs for BN medication should be considered in the design and development of interventions.
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