Abstract
RATIONALE: Prescription formularies specify which medications are available to patients. Formularies change frequently, potentially forcing patients to switch medications for nonclinical indications (nonmedical switching). Nonmedical switching is known to impact disease control and adherence. The consequences of nonmedical switching have not been rigorously studied in COPD. METHODS: We conducted a cohort study of Veterans with COPD on inhaler therapy in January 2016 when formoterol was removed from the Department of Veterans Affairs (VA) national formulary. A 2-point difference-in-differences analysis using multivariable negative binomial and generalized linear models was performed to estimate the association of the formulary change with patient outcomes in the 6 months before and after the change. Our primary outcome was the number of COPD exacerbations in 6 months, with secondary outcomes of total health care encounters and encounter-related costs in 6 months. RESULTS: We identified 10,606 Veterans who met our inclusion criteria, of which 409 (3.9%) experienced nonmedical switching off formoterol. We did not identify a change in COPD exacerbations (-0.04 exacerbations; 95% confidence interval [CI] -0.12, 0.03) associated with the formulary change. In secondary outcome analysis, we did not observe a change in the number of health care encounters (-0.12 visits; 95% CI -1.00, 0.77) or encounter-related costs ($369; 95% CI -$1141, $1878). CONCLUSIONS: Among COPD patients on single inhaler therapy, nonmedical inhaler switches due to formulary discontinuation of formoterol were not associated with changes in COPD exacerbations, encounters, or encounter-related costs. Additional research is needed to confirm our findings in more severe disease and other settings.