Indications

Terbin tablet: Indicated for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes (Tinea Unguium). Terbin granules: Indicated in Tinea Capitis. Terbin cream: Fungal infection of the skin caused by Trichophyton, Microsporum canis, and Epidermophyton floccosum. Yeast infections of the skin caused by Candida species. Pityriasis (tinea) versicolor due to Malassezia furfur. Terbin 1% Spray: Indicated in the treatment of tinea infections of the skin and pityriasis (tinea) versicolor.

Pharmacology

Terbinafine is an allylamine antifungal that inhibits the biosynthesis of ergosterol in the fungal cell membrane by inhibiting the squalene epoxidase enzyme. This causes fungal cell death due to the accumulation of high concentrations of squalene.

Dosage and Administration

Terbinafine tablet: 
- Fingernail onychomycosis: 250 mg once daily for 6 weeks.
- Toenail onychomycosis: 250 mg once daily for 12 weeks.

Terbinafine granules (up to 6 weeks): 
- Body Weight under 25 kg: 125 mg/day
- Body Weight 25 to 35 kg: 187.5 mg/day
- Body Weight over 35 kg: 250 mg/day

Terbinafine cream and spray: Apply once or twice daily to clean, dry affected areas for 1 to 2 weeks depending on the specific infection type.

Interaction

Terbinafine is an inhibitor of the CYP450 2D6 isozyme. Co-administration with drugs metabolized by 2D6 (such as tricyclic antidepressants, SSRIs, and beta-blockers) requires careful monitoring and potential dose reduction.

Contraindications

Contraindicated in individuals with hypersensitivity to terbinafine.

Side Effects

Common side effects include gastrointestinal symptoms (diarrhea, dyspepsia, abdominal pain), liver test abnormalities, rashes, urticaria, pruritus, and taste disturbances. Rare and severe effects include hepatic injury, severe skin reactions, neutropenia, and allergic reactions.

Pregnancy and Lactation

Terbinafine tablets and cream are not recommended during pregnancy or for nursing mothers unless clearly necessary.

Precautions and Warnings

Rare cases of liver failure and serious skin reactions have been reported with terbinafine tablets. Pretreatment liver function tests (ALT and AST) are advised before initiating tablet treatment. Creams and sprays are for external use only.

Overdose Effects

Doses up to 5 grams have been taken without serious adverse reactions. Symptoms include nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache.

Storage Conditions

Store in a cool and dry place, below 30 degrees Celsius, and protect from light.