Terbinafine – A Potent Ally Against Fungal Infections

 

Learn about Terbinafine – a powerful antifungal medication used to treat skin and nail infections. This blog covers its introduction, mechanism of action, pharmacokinetics, indications, dosage, side effects, contraindications, drug interactions, brand names, and prices.

Table of Contents:

1. Introduction  

2. Mechanism of Action  

3. Pharmacokinetics and Pharmacodynamics  

4. Indications  

5. Drug of Choice  

6. Contraindications  

7. Side Effects  

8. Drug Interactions  

9. Dosage  

10. Brand Names and Price  

11. Conclusion

1. Introduction:

*Terbinafine* is a synthetic *allylamine antifungal* agent primarily used to treat dermatophyte infections affecting the skin, hair, and nails. It is available in *oral and topical* forms and is highly effective due to its fungicidal activity.

2. Mechanism of Action:

Terbinafine inhibits *squalene epoxidase*, a key enzyme in the *ergosterol biosynthesis pathway*. This results in an accumulation of squalene (toxic to fungi) and a depletion of ergosterol, leading to *fungal cell death*.

3. Pharmacokinetics and Pharmacodynamics:

- *Absorption:* ~40% bioavailability orally  

- *Distribution:* High tissue penetration, especially nails and skin  

- *Metabolism:* Hepatic via CYP enzymes  

- *Half-life:* 36 hours (oral), accumulates in nails for weeks  

- *Excretion:* Mainly via urine

4. Indications:

- *Onychomycosis (nail fungus)*  

- *Tinea corporis (body)*  

- *Tinea cruris (groin)*  

- *Tinea pedis (feet)*  

- *Tinea capitis (scalp)*  

- *Cutaneous candidiasis* (off-label)

5. Drug of Choice:

- *Onychomycosis (especially toenails)* – Oral terbinafine is the first-line treatment  

- *Tinea pedis and tinea cruris* – Topical terbinafine provides quick relief

6. Contraindications:

- Hypersensitivity to terbinafine  

- Chronic or active liver disease (for oral use)  

- Severe renal impairment  

- Caution in patients with autoimmune disorders

7. Side Effects:

Oral:

  - Headache, GI upset, rash  

  - Elevated liver enzymes  

  - Rare: hepatotoxicity, taste disturbances, visual disturbances

Topical:

  - Redness, itching, dryness, local irritation

8. Drug Interactions:

- *CYP2D6 substrates* (e.g., beta-blockers, tricyclic antidepressants): levels may be altered  

- *Cimetidine:* increases terbinafine levels  

- *Rifampin:* decreases terbinafine levels  

- Monitor with hepatotoxic drugs

9. Dosage:

Oral:  

  - Adults: 250 mg once daily for 6 weeks (fingernails) or 12 weeks (toenails)  

Topical:

  - Apply once or twice daily for 1–2 weeks depending on the infection  

- Pediatric dosage: weight-based for tinea capitis

10. Brand Names and Price:

Brand Names:

  - Lamisil®️  

  - Terbicip®️  

  - Terbinaforce®️  

  - Tergosil®️  

Price Range:

  - Oral tablets (250 mg): 1–3 per tablet  

  - Cream (15g):2–6 depending on brand

11. Conclusion:

*Terbinafine* is a highly effective antifungal with *fungicidal action*, making it the preferred treatment for *nail and skin fungal infections*. While generally well tolerated, liver function monitoring is essential with long-term oral therapy. With proper use, Terbinafine offers fast and lasting relief from stubborn fungal infections.