Terbinafine Has No Established Pulmonary Indications
Terbinafine is not indicated for pulmonary infections and should not be used for respiratory tract mycoses. The drug is exclusively indicated for superficial dermatophyte infections, primarily onychomycosis and cutaneous fungal infections 1, 2.
Primary Approved Indications
Terbinafine's established therapeutic uses are limited to:
- Onychomycosis (nail infections): 250 mg daily for 6 weeks (fingernails) or 12-16 weeks (toenails), representing the first-line treatment for dermatophyte nail infections 1, 3
- Tinea pedis, corporis, and cruris: Oral therapy at 250 mg daily or topical 1% formulations for cutaneous dermatophyte infections 2, 4
- Tinea capitis in children ≥4 years: Effective specifically against Trichophyton species (not Microsporum) 3
Why Terbinafine Is Not Used for Pulmonary Infections
The evidence reveals critical limitations:
- Lack of clinical efficacy data: While in vitro studies show terbinafine has activity against Aspergillus and other molds, there are no controlled trials or guideline recommendations supporting its use in pulmonary aspergillosis or other respiratory mycoses 5, 6
- Poor activity against relevant pathogens: Terbinafine demonstrates the lowest activity against nondermatophyte moulds compared to other antifungals, with particularly poor susceptibility noted for Fusarium and Acremonium species 1
- Limited systemic mycosis evidence: Although case reports suggest potential efficacy in pulmonary aspergillosis, chromoblastomycosis, and histoplasmosis, these represent experimental uses without established dosing regimens or outcome data 5, 6
Appropriate Antifungals for Pulmonary Mycoses
For pulmonary fungal infections, evidence-based alternatives include:
- Itraconazole: Demonstrates excellent susceptibility against Aspergillus and broader coverage for nondermatophyte moulds 1
- Voriconazole and posaconazole: Newer azoles with established efficacy in invasive pulmonary aspergillosis 1
- Amphotericin B: For severe systemic infections, though some in vitro data suggest potential synergy with terbinafine in combination therapy 5
Critical Clinical Caveat
The distinction between in vitro activity and clinical efficacy is paramount. While terbinafine shows broad-spectrum antifungal activity in laboratory testing against various fungi including those causing pulmonary infections, clinical efficacy does not correlate with in vitro activity for this drug 1. Using terbinafine for pulmonary indications would be off-label, unsupported by guidelines, and potentially harmful due to delayed appropriate therapy.