What is the recommended dosage of tavaborole (topical antifungal) for a patient with onychomycosis (fungal infection of the nail), considering factors such as age, weight, and impaired renal function?

Tavaborole Dosing for Onychomycosis

Apply tavaborole 5% topical solution once daily to all affected toenails for 48 weeks, using 2 drops per great toenail and 1 drop per other affected toenails, extending application to approximately 2 mm of surrounding skin. 1

Standard Dosing Regimen

• The FDA-approved dosing is tavaborole 5% solution applied once daily for 48 weeks of treatment, with efficacy assessment at week 52 (4 weeks post-treatment). 1

• For great toenails, apply 2 drops of solution; for other affected toenails, apply 1 drop per nail. 1

• The solution should be applied to the entire nail plate and approximately 2 mm of surrounding skin. 1

Dosing Considerations by Patient Factors

Age-Related Dosing

• Tavaborole is approved for patients 6 years of age and older, with no dosage adjustment required based on age. 1

• In pediatric patients aged 6 to <17 years, the same once-daily dosing regimen is used (2 drops per great toenail, 1 drop per other affected toenails) for 48 weeks. 2

• No dosage adjustments are necessary for geriatric patients, as clinical trials showed no differences in safety or effectiveness between elderly subjects (≥65 years) and younger patients. 1

Weight-Based Considerations

• No weight-based dosing adjustments are required for tavaborole, as it is a topical agent with minimal systemic absorption. 1

• Pharmacokinetic studies demonstrated mean peak plasma concentrations of only 5.2 ± 3.5 ng/mL after 2 weeks of daily dosing, indicating negligible systemic exposure. 1

Renal Function

• No dosage adjustment is necessary for patients with impaired renal function. 1

• Although renal excretion is the major route of elimination for tavaborole metabolites, the minimal systemic absorption from topical application makes renal impairment clinically irrelevant for dosing decisions. 1

• This represents a significant advantage over systemic antifungals like terbinafine and fluconazole, which require caution or dose adjustment in renal impairment. 3

Clinical Context and Treatment Expectations

• Tavaborole achieved complete cure rates (clear nail plus negative mycology) of 6.5-9.1% versus 0.5-1.5% with vehicle in Phase III trials, with mycological cure rates of 31.1-35.9%. 1

• The relatively modest complete cure rates are consistent with other topical antifungals and reflect the inherent difficulty of treating onychomycosis topically. 4

• Treatment duration of 48 weeks is necessary because the medication must be applied throughout the time required for a healthy nail to grow out and replace the infected nail. 4, 5

Important Clinical Pitfalls

• Do not discontinue treatment prematurely—the full 48-week course is essential even if clinical improvement appears earlier, as mycological cure lags behind visible improvement. 1, 4

• Tavaborole is most appropriate for distal subungual onychomycosis with 20-60% nail involvement without dermatophytomas or lunula (matrix) involvement, as these were the inclusion criteria for efficacy trials. 1

• The most common treatment-emergent adverse events include ingrown toenail, exfoliation, erythema, and dermatitis, though discontinuation rates are low. 1, 4

• Unlike systemic antifungals, tavaborole requires no baseline laboratory monitoring (liver function tests, complete blood count) and has no significant drug interactions via CYP450 enzymes. 1