Terbinafine is the first?line oral antifungal for onychomycosis and many fungal infections of the feet, including tinea pedis, because it delivers the highest cure rates, has a shorter treatment duration, and directly targets dermatophytes—the fungi responsible for most nail and skin infections of the feet.

Terbinafine for Onychomycosis and Fungal Foot Infections

Overview

Terbinafine is an allylamine antifungal that inhibits squalene epoxidase, an enzyme essential for fungal cell membrane synthesis. This leads to fungal cell death, making terbinafine fungicidal against dermatophytes—the organisms responsible for onychomycosis and tinea pedis. Its fungicidal action distinguishes it from azole antifungals, which are typically fungistatic.

Why Terbinafine Is First?Line for Onychomycosis

Oral terbinafine is recommended as the preferred treatment for most patients with toenail fungus because it consistently outperforms alternatives in clinical cure rates.

Effectiveness

• Terbinafine has the highest effectiveness of any available therapy for onychomycosis.
• Typical cure rates range from 38–76%, depending on infection severity and nail involvement.
• It is especially effective against Trichophyton rubrum, the most common dermatophyte causing nail infections.

Treatment Duration

• Fingernails: 6 weeks
• Toenails: 12 weeks
• Full nail regrowth may take 4–18 months, depending on nail growth rate.

Dosing

• Standard dose: 250 mg once daily.
• Longer courses may be required for severe or resistant infections.

When Terbinafine Is Preferred

• Dermatophyte infections (60–90% of nail infections).
• Moderate to severe onychomycosis.
• Multiple nails involved.
• Nail matrix involvement.
• When rapid and durable cure is desired.

Terbinafine for Tinea Pedis (Athlete’s Foot)

• 

Tinea pedis is the most common fungal infection of the feet, often caused by the same dermatophytes responsible for nail infections. Terbinafine is effective both topically and orally, depending on severity.

Topical Terbinafine

• Applied once or twice daily for 1–4 weeks.
• Effective for interdigital, moccasin, and vesiculobullous types of tinea pedis.
• A one?week course of terbinafine 1% cream can be effective for mild interdigital infections.

Oral Terbinafine

Used when:

• Topical therapy fails.
• Infection is extensive or chronic.
• Hyperkeratotic (moccasin?type) tinea pedis is present.
• Coexisting onychomycosis is contributing to reinfection.

Mechanism of Action

Terbinafine inhibits squalene epoxidase, causing toxic accumulation of squalene and depletion of ergosterol in fungal cell membranes. This fungicidal action is particularly effective against dermatophytes, explaining its superior performance in nail and foot infections.

Safety, Monitoring, and Contraindications

Although generally well tolerated, terbinafine requires monitoring due to potential systemic effects.

Common Side Effects

• Gastrointestinal upset
• Headache
• Rash
• Taste disturbance

Serious but Rare Effects

• Hepatotoxicity
• Blood dyscrasias
• Severe skin reactions

Monitoring

• Baseline liver function tests (LFTs)
• Repeat LFTs at 4–6 weeks for oral therapy
• Avoid in severe hepatic impairment or severe renal impairment (CrCl < 20 mL/min).

Drug Interactions

Patients taking terbinafine with:

• SSRIs
• TCAs
• Beta blockers
• Atypical antipsychotics
• Tamoxifen should be monitored for interactions.

Comparison With Other Antifungals

Treatment	Best For	Effectiveness	Duration	Notes
Terbinafine	Dermatophyte nail & foot infections	Highest	6–12 weeks	First?line; requires LFT monitoring
Itraconazole	Yeast infections, some dermatophytes	Moderate	Pulse or continuous	Avoid in heart failure; more interactions
Fluconazole	Yeasts	Lower	Weekly dosing for months	Alternative when terbinafine not tolerated
Topical agents	Mild infections	Lower	Daily for up to 1 year	Useful when oral therapy contraindicated

Preventing Reinfection

Because relapse rates can reach 25%, prevention is essential.

Key strategies:

• Keep feet dry; dry between toes thoroughly.
• Use antifungal powders in shoes.
• Avoid occlusive footwear.
• Wear sandals in communal showers.
• Treat coexisting tinea pedis to prevent reinfection of nails.

Clinical Significance

Onychomycosis and tinea pedis are not merely cosmetic problems—they can cause pain, impaired mobility, secondary bacterial infections, and reduced quality of life. Terbinafine’s ability to eradicate dermatophytes makes it a cornerstone therapy for restoring nail integrity, reducing symptoms, and preventing recurrence.

Terbinafine remains the gold standard for treating onychomycosis and fungal infections of the feet due to its fungicidal action, high cure rates, and relatively short treatment duration. When used appropriately—with proper diagnosis, monitoring, and preventive measures—it offers the most reliable pathway to full resolution of fungal nail and skin infections.