Risk of Psoriasis Following Terbinafine or Itraconazole Treatment for Onychomycosis: A Population-Based Case-Control Comparative Study

Introduction: Several case studies have reported an association between antifungal drug use and psoriasis risk. Objective: The objective of this study was to investigate the association between terbinafine/itraconazole exposure and psoriasis incidence. Methods: Among patients with onychomycosis in the Taiwan National Health Insurance Research Database, 3831 incident psoriasis cases were identified during 2004–2010 and compared with 3831 age- and sex-matched controls with the same look-back period. Multivariate conditional logistic regression was used for the analysis. Results: The psoriasis cases were significantly more likely than matched controls to have used terbinafine or itraconazole (59.85 vs. 42.70%, respectively; p < 0.0001). After adjusting for potential confounders and cumulative duration of antifungal drug prescription, terbinafine/itraconazole use was associated with an increased psoriasis risk (adjusted odds ratio 1.33, 95% confidence interval 1.15–1.54). The association was stronger for more recent drug exposure (adjusted odds ratio 2.96, 95% confidence interval 2.25–3.90 for ≤ 90 days before the sampling date; adjusted odds ratio 1.04, 95% confidence interval 0.89–1.22 for > 360 days). In a comparison of patients receiving terbinafine or itraconazole only, psoriasis risk was higher for itraconazole (adjusted odds ratio 1.21, 95% confidence interval 1.05–1.40). Conclusion: This large population-based case-control analysis showed that exposure to terbinafine or itraconazole is associated with an increased risk of incident psoriasis. The finding of an increased psoriasis risk for antifungal drug users, particularly for itraconazole, deserves attention in clinical practice although further prospective studies are necessary to confirm our findings and clarify the biological mechanisms that underlie these associations.