IntroductionThere are limited data on the effects of forced medication switching for a nonmedical reason in patients with obstructive airway conditions. This study evaluated disruption in care resulting from a nonmedical medication switch for patients with asthma and/or chronic obstructive pulmonary disease who previously received the inhaled corticosteroid/long-acting β2-agonist budesonide/formoterol.MethodsThis retrospective pharmacy benefit prescription claims analysis evaluated Medicare Part D patients who filled a prescription for budesonide/formoterol as their last inhaled corticosteroid/long-acting β2-agonist in 2016 and were affected by a formulary block of budesonide/formoterol in 2017. Changes to respiratory maintenance therapy, length of gaps in care during which a patient was not in possession of a respiratory controller medication, acute medication use indicative of disease exacerbations, and medication adherence were assessed.ResultsA total of 42,553 patients were included in the analysis. Following the formulary block, 30,016 patients (71%) switched to another controller; 20,628 of these patients (69%) switched to a new inhaled corticosteroid/long-acting β2-agonist, 7081 (23%) stepped down to a monotherapy, and 2307 (8%) switched to a non-inhaled corticosteroid-containing controller. Despite the formulary block, 22,903 patients (54%) attempted to fill budesonide/formoterol as their first postblock controller, and 6624 patients (16%) attempted to return to budesonide/formoterol after switching to another controller. On average, patients experienced a gap in care of approximately 4 months without a controller medication. Also, 9674 (23%) did not fill any controller over the 1-year postblock period. Of those patients who experienced a gap in care, 14,926 (47%) filled a prescription indicative of a possible exacerbation during the gap period (i.e., oral corticosteroids for patients with asthma and oral corticosteroids and/or antibiotics for patients with chronic obstructive pulmonary disease).ConclusionsThe Medicare Part D formulary block was associated with disruption in the management of patients’ respiratory conditions and may have adversely impacted disease control.Supplementary InformationThe online version contains supplementary material available at 10.1007/s41030-021-00147-8.