Efficacy and Safety of Voriconazole for Difficult-to-Treat Distal Lateral Subungual Onychomycosis (DLSO)

This retrospective case series evaluated off-label voriconazole for distal lateral subungual onychomycosis (DLSO) unresponsive to standard therapy. Twenty-nine culture-confirmed patients who had failed terbinafine (250 mg daily × 12 weeks) and itraconazole pulses (200 mg twice daily for 1 week/month × 3) received voriconazole (200 mg twice on day 1, then 200 mg daily for 3-4 months). Assessments occurred at 2, 4, 6-9, and 12 months; the primary endpoint was combined clinical cure (≥90% nail clearance) plus mycological cure (negative KOH and culture) at 12 months. Intention-to-treat included 29 patients; per-protocol included 27 (two did not complete follow-up). In the per-protocol cohort, combined cure was 55.6% (15/27) and mycological cure 74.1% (20/27). Complete clinical cure occurred in 66.7% (18/27); 25.9% (7/27) improved markedly, 3.7% (1/27) mildly, and 3.7% (1/27) showed no improvement. Voriconazole was well tolerated and may be considered for DLSO refractory to terbinafine ± itraconazole. Antifungal stewardship remains essential.