Monthly Usage of Efinaconazole 10% Solution in Two Phase 3 Randomized Trials: Is One 4-mL Bottle Enough for Proper Treatment?

Introduction: In onychomycosis management, excellent treatment adherence is necessary, and requires adequate medication supply. Efinaconazole 10% topical solution is available in 4- or 8-mL bottles; lacking published guidance, 4 mL is most often prescribed. The objective of this analysis was to use clinical data to determine monthly efinaconazole usage by patient demographics and clinical characteristics. Methods: In two identical, double-blind, phase 3 studies, adult participants with mild-to-moderate onychomycosis affecting 20-50% of ≥1 great (target) toenail were randomized 3:1 to once-daily treatment with efinaconazole 10% solution or vehicle for 48 weeks. Bottles of study product were weighed upon dispensation at each study visit (every 4 weeks) and upon return at the following visit. Monthly at-home efinaconazole use was analyzed post hoc based on number of affected toenails, percent involvement of the target toenail, body mass index (BMI), and sex. Results: Efinaconazole-treated participants in both studies (n=656 and 580) had on average 3.7-3.8 affected toenails. Among those with usage data (n=1067), over 55% had ≥4 affected toenails. For the 90% of participants with ≥2 affected nails, average usage ranged from 4.39-6.36 mL/month, corresponding to 1.10-1.59 4-mL bottles; only the 10% of participants with one affected toenail used <4 mL of efinaconazole monthly. Additional subgroup analyses revealed no meaningful differences in efinaconazole usage based on target toenail involvement, BMI, or sex; average medication use was 4.69-5.29 mL/month, corresponding to 1.17-1.32 4-mL bottles monthly. Conclusions: Given that the 4-mL bottle of efinaconazole is most commonly prescribed, patients with onychomycosis of ≥2 toenails will likely run out of medication in under a month. This can lead to gaps in onychomycosis treatment, which may affect medication efficacy and increase likelihood of relapse or reinfection. The number of affected nails should be the major consideration when determining the monthly efinaconazole quantity to prescribe. Funding: Ortho Dermatologics