From the Guidelines
Yes, terbinafine is a fungicidal medication, meaning it kills fungi rather than just inhibiting their growth. Terbinafine works by inhibiting the enzyme squalene epoxidase, which disrupts ergosterol synthesis in the fungal cell membrane. This leads to accumulation of squalene inside fungal cells and ultimately causes cell death. Terbinafine is particularly effective against dermatophytes (the fungi that cause conditions like athlete's foot, ringworm, and nail infections) and demonstrates strong fungicidal activity against these organisms, as shown in a study published in the British Journal of Dermatology 1.
Key Points
- Terbinafine's fungicidal nature contributes to its clinical effectiveness and relatively low relapse rates compared to some fungistatic alternatives.
- It's available in both topical forms (creams, gels) for skin infections and oral tablets (typically 250mg daily) for more severe or nail infections.
- Oral terbinafine treatment typically requires 6 weeks for fingernail infections and 12 weeks for toenail infections to achieve complete eradication, as recommended by the British Association of Dermatologists' guidelines for the management of onychomycosis 2014 1.
- The minimum inhibitory concentration (MIC) of terbinafine is very low, approximately 0.004 µg mL–1, which is equivalent to the minimal fungicidal concentration (MFC), demonstrating that this drug is truly fungicidal in vitro 1.
Clinical Effectiveness
Terbinafine has been shown to be more effective than itraconazole for onychomycosis caused by dermatophytes, with higher cure rates and lower relapse rates, as demonstrated in a multicentre, randomized trial involving 508 subjects 1.
Treatment Recommendations
Terbinafine should be considered as the first-line treatment for dermatophyte onychomycosis, unless there are contraindications, due to its higher efficacy and tolerability compared to itraconazole 1.
From the FDA Drug Label
Depending on the concentration of the drug and the fungal species test in vitro, terbinafine may be fungicidal. The answer to whether terbinafine is fungicidal is: it may be fungicidal, depending on the concentration of the drug and the fungal species. 2
From the Research
Terbinafine's Mechanism of Action
- Terbinafine inhibits the biosynthesis of ergosterol, a principal sterol in fungi, at the level of squalene epoxidase 3.
- This inhibition results in ergosterol-depleted fungal cell membranes, which has a fungistatic effect, and the toxic accumulation of intracellular squalene, which has a fungicidal effect 3.
Fungicidal Activity of Terbinafine
- Terbinafine has demonstrated excellent fungicidal activity against dermatophytes and variable activity against yeasts and non-dermatophyte molds in vitro 3.
- The drug has fungicidal activity against dermatophytes, molds, and certain dimorphic fungi, and fungistatic activity against Candida albicans 4.
- Terbinafine's MIC against dermatophytes is the lowest of all currently available systemic antifungal agents, and its MIC:MFC ratio is 1:1, indicating that it should be effective over short treatment durations 5.
Clinical Efficacy of Terbinafine
- Terbinafine is effective in the treatment of onychomycosis, with cure rates ranging from 67% to 85% in clinical trials 6.
- The drug is also effective against other fungal infections, including tinea corporis, tinea pedis, and cutaneous candidiasis 5, 7.
- Terbinafine has a low rate of relapse of infection after cure of chronic dermatophyte infections, which is a recognized problem with other antifungal drugs 7.