Inhaler Formulary Change in COPD and the Association with Exacerbations, Health Care Utilization, and Costs.

Prescription formularies specify which medications are available to patients. Formularies change frequently, potentially forcing patients to switch medications for non-clinical indications ("non-medical switching"). Non-medical switching is known to impact disease control and adherence. The consequences of non-medical switching have not been rigorously studied in COPD. 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 two-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. We identified 10,606 Veterans who met our inclusion criteria, of which 409 (3.9%) Veterans experienced non-medical switching off formoterol. We did not identify a change in COPD exacerbations (-0.04 exacerbations; 95%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). Among COPD patients on single inhaler therapy,non-medical inhaler switches due to formulary discontinuation of formoterol was 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.

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