Indications

• Dermafin Tablet: For the treatment of onychomycosis (fungal infections) of the toenail or fingernail caused by dermatophytes.
• Dermafin Granules: For the treatment of tinea capitis (ringworm of the scalp).
• Dermafin Cream: For fungal skin infections caused by Trichophyton species,Microsporum canis, and Epidermophyton floccosum. Also for yeast infections caused by Candida and pityriasis versicolor due to Malassezia furfur.
• Dermafin 1% Spray: For the treatment of tinea skin infections and pityriasis versicolor.

Pharmacology

Terbinafine is an allylamine antifungal that inhibits the biosynthesis of ergosterol, an essential component of fungal cell membranes. It does this by inhibiting the squalene epoxidase enzyme. This inhibition leads to the accumulation of high concentrations of squalene, which increases membrane permeability and causes fungal cell death.

Dosage & Administration

• Terbinafine Tablet:
  • Fingernail onychomycosis: 250 mg once daily for 6 weeks.
  • Toenail onychomycosis: 250 mg once daily for 12 weeks.
• Terbinafine Granules:
  • Body weight < 25 kg: 125 mg/day for up to 6 weeks.
  • Body weight 25-35 kg: 187.5 mg/day for up to 6 weeks.
  • Body weight > 35 kg: 250 mg/day for up to 6 weeks.
• Terbinafine Cream: Applied once or twice daily. The duration of treatment is typically 1-2 weeks for tinea corporis/cruris and 1 week for tinea pedis. For cutaneous candidiasis and pityriasis versicolor, treatment is typically 2 weeks. The affected areas should be cleansed and dried before application.
• Terbinafine 1% Spray: Applied once or twice daily. Duration of treatment is typically 1 week for tinea pedis and tinea corporis/cruris, and 1 week (twice daily) for pityriasis versicolor.

Interaction

Terbinafine is a CYP450 2D6 isozyme inhibitor. Co-administration with drugs metabolized by this enzyme (e.g., tricyclic antidepressants, SSRIs, beta-blockers, some antiarrhythmics) may require careful monitoring and a dose reduction of the other drug.

Contraindications

Terbinafine tablets and cream are contraindicated in individuals hypersensitive to terbinafine.

Side Effects

Common side effects include gastrointestinal symptoms (diarrhea, dyspepsia, abdominal pain), abnormal liver tests, rashes, and taste disturbances. Rare but serious side effects include liver failure, severe skin reactions (Stevens-Johnson Syndrome), severe neutropenia, thrombocytopenia, and allergic reactions. Other reported side effects include fatigue, vomiting, joint pain, muscle pain, and hair loss.

Pregnancy & Lactation

Terbinafine tablets should not be initiated during pregnancy, as there are no adequate and well-controlled studies in pregnant women. Terbinafine is present in breast milk, so treatment is not recommended for nursing mothers. The cream should also not be used in pregnancy or by breastfeeding mothers unless the potential benefits outweigh the risks.

Precautions & Warnings

• Liver Disease: Rare cases of liver failure have occurred. Terbinafine tablets are not recommended for patients with chronic or active liver disease. Pre-treatment serum transaminase tests (ALT and AST) are advised for all patients taking the tablets. The drug should be discontinued if there is any evidence of liver injury.
• Skin Reactions: In case of a progressive skin rash, treatment should be discontinued.
• External Use: The cream is for external use only and contact with the eyes should be avoided.

Overdose Effects

Overdose symptoms are limited but may include nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache. Doses up to 5 grams have been taken without serious adverse reactions.

Therapeutic Class

Terbinafine is an antifungal preparation, both for oral and topical use.