Polypharmacy in US Medicare beneficiaries with antineutrophil cytoplasmic antibody vasculitis

BACKGROUND: Treatment requirements of antineutrophil cytoplasmic autoantibody vasculitis (AV) and high comorbidity burden among patients with AV may lead to higher potential for polypharmacy and its associated adverse outcomes, including adverse drug events, nonadherence, drug-drug interactions, and higher costs. Medication burden and risk factors associated with polypharmacy in patients with AV have not been well-characterized. OBJECTIVE: To characterize medication burden and examine prevalence of and risk factors for polypharmacy in the first year after diagnosis with AV. METHODS: We conducted a retrospective cohort study using 2015-2017 Medicare claims to identify incident cases of AV. We counted the number of unique generic products dispensed to patients in each of the 4 quarters after diagnosis and categorized medication count as high (≥10 medications), moderate (5-9 medications), or minimal or no polypharmacy (<5 medications). We used multinomial logistic regression to examine associations of predisposing, enabling, and medical need factors with having high or moderate polypharmacy. RESULTS: In 1,239 Medicare beneficiaries with AV, high or moderate polypharmacy was most common in the first quarter after diagnosis (83.7%), with 43.2% taking 5 - 9 medications and 40.5% taking at least 10. The odds of high polypharmacy were greater in all quarters for patients with eosinophilic granulomatosis with polyangiitis compared with granulomatosis with polyangiitis, ranging from 2.02 (95% CI = 1.18 - 3.46) in the third quarter to 2.96 (95% CI = 1.64-5.33) in the second quarter. Older age, diabetes, chronic kidney disease, obesity, a higher Charlson Comorbidity Index score, coverage with Medicaid/Part D low-income subsidy, and living in areas with low education or persistent poverty were risk factors for high or moderate polypharmacy. CONCLUSIONS: Medicare beneficiaries with newly diagnosed AV experienced a high medication burden, with more than 40% taking at least 10 medications and the highest rates among those with eosinophilic granulomatosis with polyangiitis. Patients with AV may benefit from medication therapy management interventions to manage complex drug regimens and reduce risks associated with polypharmacy.