Terbinafine is a synthetic allylamine antifungal agent, available as a 500mg oral tablet. It is fungicidal and is considered a first-line systemic treatment for dermatophyte infections (onychomycosis, tinea capitis, tinea corporis) in India due to its high efficacy, favorable pharmacokinetics, and cost-effectiveness in generic forms. It works by inhibiting squalene epoxidase, a key enzyme in fungal ergosterol synthesis.
Adult: Onychomycosis: 500mg once daily. Fingernails: 6 weeks. Toenails: 12 weeks. Tinea Capitis/Corporis: 250mg once daily for 2-4 weeks; severe cases may require 500mg daily.
Note: Take tablet with a full glass of water. Can be taken with or without food, but taking with food may improve tolerance and slightly increase absorption. Swallow whole; do not crush or chew.
Terbinafine is a fungicidal agent that selectively inhibits the fungal enzyme squalene epoxidase. This inhibition occurs early in the ergosterol biosynthesis pathway. Ergosterol is a critical component of the fungal cell membrane, providing structural integrity and function.
Pregnancy: Category B (US FDA). Not recommended during pregnancy. Use only if potential benefit justifies potential risk to the fetus. Terbinafine is transferred across the placenta. Limited human data.
Driving: May cause dizziness, visual disturbances. Patients should be cautious until their response is known.
| Rifampicin | Induces CYP enzymes, increasing terbinafine clearance and reducing plasma levels by ~50%. May lead to therapeutic failure. | Major |
| Cimetidine | Inhibits CYP enzymes, decreases terbinafine clearance, increasing plasma levels by ~33%. Risk of increased side effects. | Moderate |
| SSRIs (e.g., Sertraline, Paroxetine) | Terbinafine is a potent inhibitor of CYP2D6. Increases plasma levels of CYP2D6 substrates (many SSRIs, TCAs, beta-blockers like metoprolol, codeine). Can lead to toxicity of the co-administered drug. | Major |
| Warfarin | Potential interaction via CYP inhibition. Monitor INR closely as terbinafine may potentiate warfarin effect. | Moderate |
| Cyclosporine | Terbinafine may reduce cyclosporine metabolism, increasing its levels. Monitor cyclosporine levels and renal function. | Moderate |
| Oral Contraceptives | No clinically significant interaction reported. Efficacy not affected. | Minor |