Background: Nonadherence to systemic treatments for psoriasis leads to treatment failure and increased health care utilization. Objective: Examine drug utilization patterns and adherence of new users of systemic medications for psoriasis. Methods: We conducted a retrospective, comparative cohort study using a large US health insurance claims database including psoriasis patients who were new users of acitretin, adalimumab, etanercept, methotrexate, or ustekinumab. Adherence was measured by using proportion of days covered dichotomized as adherent (≥0.80) or nonadherent (<0.80). Odds ratios (ORs) and 95% confidence intervals (CIs) comparing adherence to each exposure (acitretin, adalimumab, etanercept, or ustekinumab) to the referent (methotrexate) were estimated via logistic regression, with pairwise 1:1 propensity score matching to adjust for potential confounders. Results: In total, 22,742 patients were new users of systemic medications. Among these patients, adherence to adalimumab (OR 2.24, 95% CI 2.05-2.45); etanercept (OR 1.77, 95% CI 1.63-1.92); and ustekinumab (OR 2.54, 95% CI 2.24-2.87) was greater and acitretin (OR 0.57, 95% CI 0.50-0.63) lower compared with methotrexate. Limitations: Unable to evaluate reasons for discontinuation. Conclusion: We report greater adherence to biologics than methotrexate in new users. Further research is needed to understand overall low adherence to systemic medications for psoriasis.
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