Terbinafine

1. Introduction

Terbinafine is a broad-spectrum antifungal agent used to treat fungal infections of the skin, nails, and scalp. It works by inhibiting squalene epoxidase, an enzyme necessary for fungal cell membrane synthesis, leading to fungal cell death.

2. Indications

  • Onychomycosis (Fungal Nail Infections): Treatment of fingernail and toenail infections caused by dermatophytes.
  • Tinea Infections (Skin Fungal Infections): Including tinea pedis (athlete’s foot), tinea cruris (jock itch), and tinea corporis (ringworm).
  • Tinea Capitis (Scalp Ringworm): Common in children.

3. Dosage

Adults:

  • Onychomycosis (Nail Fungal Infection):
    • 250 mg once daily for 6 weeks (fingernails) or 12 weeks (toenails).
  • Tinea Pedis, Tinea Cruris, Tinea Corporis:
    • 250 mg once daily for 2–6 weeks, depending on severity.
  • Tinea Capitis (Scalp Ringworm):
    • 250 mg once daily for 4–6 weeks.

Children:

  • Tinea Capitis (Scalp Ringworm):
    • 10–20 kg: 62.5 mg once daily
    • 20–40 kg: 125 mg once daily
    • >40 kg: 250 mg once daily
    • Duration: 4–6 weeks.

Elderly:

  • No dose adjustment required, but monitor liver function.

Renal Impairment:

  • CrCl <50 mL/min: Use with caution; dose reduction may be needed.

Hepatic Impairment:

  • Avoid use in severe hepatic impairment due to risk of liver toxicity.

4. Administration

  • Tablets: Take with or without food.
  • Topical Cream: Apply once or twice daily to the affected area and rub gently.
  • Topical Spray/Gel: Apply once daily to the affected area.

5. Forms Available

  • Tablets: 250 mg
  • Topical Cream: 1%
  • Topical Spray: 1%
  • Oral Granules (for paediatric use): 125 mg/packet

6. Side Effects

6.1 Common Side Effects:

  • Nausea
  • Diarrhoea
  • Taste disturbances (dysgeusia)
  • Headache
  • Rash

6.2 Less Common Side Effects:

  • Fatigue
  • Itching (pruritus)
  • Abdominal pain

6.3 Rare but Serious Side Effects:

  • Hepatotoxicity (liver toxicity): Jaundice, elevated liver enzymes, liver failure (discontinue immediately if symptoms appear).
  • Severe skin reactions: Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN).
  • Blood disorders: Neutropenia, thrombocytopenia.

7. Warnings

  • Liver Toxicity: Avoid in patients with pre-existing liver disease; monitor liver function before and during treatment.
  • Taste & Smell Disturbances: Can be permanent in some cases.
  • Severe Skin Reactions: Discontinue if signs of rash, blistering, or peeling occur.
  • Hematological Effects: Rare cases of neutropenia and thrombocytopenia reported.

8. Precautions

  • Monitor liver function (ALT, AST) before and during treatment.
  • Use with caution in patients with psoriasis, as terbinafine may worsen the condition.
  • Avoid alcohol during treatment to reduce liver toxicity risk.

9. Interactions

  • CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine): May increase terbinafine levels.
  • CYP2D6 Substrates (e.g., tricyclic antidepressants, beta-blockers, antipsychotics): Terbinafine may alter their metabolism.
  • Warfarin: May increase bleeding risk.
  • Caffeine: Terbinafine reduces caffeine clearance, leading to prolonged effects.

10. Monitoring Parameters

  • Liver function tests (LFTs): Baseline and after 4–6 weeks of treatment.
  • Complete blood count (CBC): If symptoms of blood disorders appear.
  • Taste and smell disturbances: If persistent, discontinue therapy.

11. Use in Children

  • Approved for tinea capitis in children >4 years.
  • Requires weight-based dosing.

12. Use in Pregnancy

  • Category B: Animal studies show no harm, but human data is limited.
  • Avoid unless clearly needed.

13. Use in Elderly

  • No dose adjustment required, but monitor liver function closely.

14. Use in Kidney Disease

  • Use with caution in CrCl <50 mL/min.
  • Dose reduction may be necessary.

15. Use in Liver Disease

  • Contraindicated in severe hepatic impairment.
  • Monitor liver function in all patients taking oral terbinafine.

16. Patient Counselling Points

  • Complete the full course of treatment, even if symptoms improve.
  • Monitor for liver toxicity: Report jaundice, dark urine, pale stools, or abdominal pain.
  • Taste changes may occur: If persistent, discontinue the medication.
  • Avoid alcohol during treatment.
  • For topical use: Apply only to affected areas; wash hands after application.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
LamisilNovartis250 mg Tablet$200 (30 tablets)
TerbinafineVarious Generic250 mg Tablet$40 (30 tablets)
Lamisil AT CreamNovartis1% Cream (15g)$15 (1 tube)

18. 15 FAQs (Frequently Asked Questions)

1. What is Terbinafine used for?
It treats fungal infections of nails, skin (ringworm, athlete’s foot, jock itch), and scalp.

2. How long does Terbinafine take to work?

  • Skin infections: 2–6 weeks.
  • Nail infections: 6–12 weeks, with full nail regrowth taking 6–12 months.

3. Can Terbinafine cause liver damage?
Yes, regular liver function tests are required during treatment.

4. Can I drink alcohol while taking Terbinafine?
Avoid alcohol, as it increases the risk of liver toxicity.

5. Can Terbinafine cause loss of taste or smell?
Yes, some patients report temporary or permanent taste and smell disturbances.

6. Can I stop taking Terbinafine once my symptoms improve?
No, complete the full course to prevent recurrence.

7. Can Terbinafine be taken on an empty stomach?
Yes, it can be taken with or without food.

8. Can pregnant women take Terbinafine?
It is not recommended during pregnancy unless essential.

9. Can Terbinafine be used in children?
Yes, it is approved for tinea capitis in children >4 years.

10. Can I use Terbinafine for a yeast infection?
No, it is not effective against Candida infections (e.g., oral/vaginal thrush).

11. Can Terbinafine be used long-term?
Yes, but long-term use requires liver monitoring.

12. Does Terbinafine interact with caffeine?
Yes, it slows caffeine breakdown, leading to prolonged effects.

13. Can Terbinafine cause a rash?
Yes, discontinue if severe rash or allergic reaction occurs.

14. Can Terbinafine be used for athlete’s foot?
Yes, topical or oral terbinafine can treat athlete’s foot.

15. How should Terbinafine be stored?
Store at room temperature, away from moisture and heat.