Indications:

Tablet: Onychomycosis of toenail or fingernail due to dermatophytes (Tinea unguium).
Granules: Tinea capitis.
Cream: Fungal infections of the skin caused by Trichophyton spp., Microsporum canis, Epidermophyton floccosum; yeast infections (e.g. Candida albicans); Pityriasis versicolor.
Spray (1%): Tinea infections of the skin and pityriasis versicolor due to Malassezia furfur.

Pharmacology: Terbinafine is an allylamine antifungal that inhibits squalene epoxidase, blocking ergosterol biosynthesis. This leads to accumulation of squalene, increased membrane permeability, and fungal cell death. Active against Trichophyton rubrum, T. mentagrophytes, and related species.

Dosage & Administration:

Tablet:
- Fingernail onychomycosis: 250 mg daily for 6 weeks.
- Toenail onychomycosis: 250 mg daily for 12 weeks.
- Clinical effect appears months later as healthy nail grows out.
Granules (by body weight):
- <25 kg: 125 mg/day, up to 6 weeks.
- 25–35 kg: 187.5 mg/day, up to 6 weeks.
- 35 kg: 250 mg/day, up to 6 weeks.
Cream:
- Apply once or twice daily to clean, dry skin.
- Tinea corporis/cruris: 1–2 weeks.
- Tinea pedis: 1 week.
- Cutaneous candidiasis: 2 weeks.
- Pityriasis versicolor: 2 weeks.
Spray (1%):
- Tinea pedis: once daily, 1 week.
- Tinea corporis/cruris: once daily, 1 week.
- Pityriasis versicolor: twice daily, 1 week.

Interactions:

Terbinafine inhibits CYP2D6. Monitor co-administration with tricyclic antidepressants, SSRIs, beta-blockers, antiarrhythmics (flecainide, propafenone), MAO-B inhibitors.

Contraindications:

Hypersensitivity to terbinafine.

Side Effects:

GI upset, liver enzyme abnormalities, rash, urticaria, pruritus, taste disturbances.
Rare: hepatic injury, liver failure, Stevens-Johnson syndrome, toxic epidermal necrolysis, neutropenia, thrombocytopenia, angioedema, anaphylaxis.

Pregnancy & Lactation:

Tablets: Not recommended during pregnancy or lactation.
Cream/Spray: Limited data; avoid unless benefits outweigh risks. Terbinafine is excreted in breast milk.

Precautions & Warnings:

Monitor liver function before and during tablet therapy.
Discontinue if signs of hepatotoxicity or severe skin reactions occur.
Cream/Spray: External use only, avoid eye contact.

Overdose Effects:

Tablets: Limited data; symptoms include nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, headache.
Cream/Spray: Excess topical use may cause local irritation.