Terbinafine: Comprehensive Clinical Guide

Oral Terbinafine Dosing for Onychomycosis

For adults with dermatophyte onychomycosis, oral terbinafine 250 mg once daily is the first-line treatment: 6 weeks for fingernail infections and 12 weeks for toenail infections. 1

Standard Adult Dosing

Fingernail onychomycosis: 250 mg once daily for 6 weeks 1
Toenail onychomycosis: 250 mg once daily for 12 weeks 1
Severe toenail cases: May extend to 16 weeks 2
Administration: May be taken with or without food 2

Pediatric Weight-Based Dosing

< 20 kg: 62.5 mg daily 3, 4
20–40 kg: 125 mg daily 3, 4
> 40 kg: 250 mg daily 3, 4
Duration: 6 weeks for fingernails, 12 weeks for toenails 3, 4

Terbinafine is generally preferred over itraconazole in children despite both having equal strength recommendations, because terbinafine achieves 46% long-term mycological cure versus 13% for itraconazole, with lower relapse rates (23% vs 53%). 4

Pre-Treatment Requirements

Mandatory Baseline Testing

Mycological confirmation: KOH preparation, fungal culture, or nail biopsy must be obtained before initiating therapy to avoid treating non-fungal nail dystrophies 1, 2
Liver function tests: Measure ALT and AST before starting treatment 1, 5, 2
Complete blood count: Obtain baseline CBC 3, 4, 5

Household Screening

Examine all family members for onychomycosis and tinea pedis, as intra-household transmission is common and concurrent treatment of all infected individuals is necessary 4
Check the affected patient for concomitant tinea capitis and tinea pedis 4

Absolute Contraindications

Terbinafine is absolutely contraindicated in the following conditions:

History of allergic reaction to oral terbinafine (risk of anaphylaxis) 1
Active or chronic liver disease 1, 5, 2
Systemic lupus erythematosus 2
Renal impairment with creatinine clearance ≤ 50 mL/min (terbinafine is primarily cleared by the kidneys) 5

Liver Function Monitoring Protocol

Standard-Risk Patients (No Pre-Existing Liver Disease)

Baseline LFTs required before starting therapy 1, 5
No routine monitoring during treatment if baseline is normal and treatment duration is ≤ 12 weeks 5
Monitor only if symptoms develop: persistent nausea, vomiting, right upper abdominal pain, jaundice, dark urine, or pale stools 1, 5

High-Risk Patients (Pre-Existing Liver Abnormalities, Heavy Alcohol Use, Hepatitis History, or Concurrent Hepatotoxic Drugs)

Week 2: Repeat LFTs 5
Weeks 2–8: Monitor every 2 weeks 5
If baseline AST/ALT ≥ 2 × ULN: Weekly monitoring for first 2 weeks, then every 2 weeks 5

Immediate Discontinuation Criteria

AST/ALT ≥ 5 × upper limit of normal 5
Rising bilirubin during treatment 5
Any clinical symptoms of hepatotoxicity (jaundice, persistent nausea, vomiting, abdominal pain, fatigue) 1, 5

Discontinue terbinafine immediately if biochemical or clinical evidence of liver injury develops. 1, 5

Alternative Systemic Therapies

First-Line Alternative: Itraconazole Pulse Therapy

When terbinafine is contraindicated or not tolerated, itraconazole pulse therapy is the preferred alternative.

Dosing: 200 mg twice daily (400 mg/day) for 1 week per month 2
Fingernails: 2 pulses (2 months total) 3, 2
Toenails: 3 pulses (3 months total) 3, 2
Administration: Take with food in an acidic gastric environment to optimize absorption 3, 4
Monitoring: Hepatic function tests required in patients with pre-existing liver abnormalities or when continuous therapy exceeds 1 month 3, 4
Contraindication: Congestive heart failure 2

Pediatric itraconazole dosing: 5 mg/kg per day for 1 week per month; 2 pulses for fingernails, 3 pulses for toenails 3, 4

Second-Line: Fluconazole

Reserved for cases where both terbinafine and itraconazole are contraindicated or not tolerated.

Adult dosing: 150–450 mg once weekly 2
Pediatric dosing: 3–6 mg/kg once weekly 3, 4
Duration (adults): Minimum 6 months, often 12–18 months for toenails 2
Duration (pediatric): 12–16 weeks for fingernails, 18–26 weeks for toenails 3, 4
Monitoring: Baseline LFTs and CBC required 3, 4
Renal adjustment: 50% dose reduction when GFR < 45 mL/min; contraindicated in severe renal impairment 5

Not Recommended: Griseofulvin

Griseofulvin is no longer a first-line option due to low efficacy (30–40% cure rate) and prolonged treatment requirements. 3, 4, 2

Pediatric dosing (if no alternatives): 10 mg/kg per day (maximum 500 mg) 3, 4
Administration: Must be taken with fatty food to increase absorption 3, 4

Renal Impairment Management

For patients with creatinine clearance ≤ 50 mL/min, terbinafine is contraindicated rather than dose-adjusted. 5

Treatment Algorithm for CKD Patients

First choice: Topical therapy
- Amorolfine 5% lacquer once or twice weekly for 6–12 months 5
- Ciclopirox 8% lacquer once daily for up to 48 weeks 5
Second choice (if systemic therapy essential): Itraconazole with normal hepatic function 5
- Requires dose adjustment when CrCl < 30 mL/min 5
Avoid: Fluconazole requires 50% dose reduction when GFR < 45 mL/min and is contraindicated in severe renal impairment 5

Adverse Effects and Management

Common Adverse Effects (> 2% of Patients)

Gastrointestinal: Nausea, diarrhea, abdominal pain, dyspepsia, flatulence (49% of reported side effects) 5, 1
Headache 3, 4, 1
Dermatologic: Rash, pruritus, urticaria, eczema (23% of reported side effects) 5, 1
Liver enzyme abnormalities 1

Serious Adverse Effects Requiring Immediate Discontinuation

Taste Disturbance (Potentially Permanent)

Can be severe enough to cause decreased food intake, weight loss, and depressive symptoms 1
May resolve within several weeks but can be prolonged (> 1 year) or permanent 5, 1
Action: Discontinue terbinafine if taste disturbance occurs 1

Smell Disturbance (Potentially Permanent)

May be prolonged (> 1 year) or permanent 1
Action: Discontinue terbinafine if smell disturbance occurs 1

Hepatotoxicity

Cases of liver failure leading to liver transplant or death have occurred 1
Rare but can occur in patients with or without pre-existing liver disease 5, 1
Action: Discontinue immediately if biochemical or clinical evidence of liver injury develops 1, 5

Severe Cutaneous Reactions

Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, exfoliative dermatitis, bullous dermatitis, DRESS syndrome 5, 1
Action: Discontinue if signs or symptoms of drug reaction occur 1

Hematologic Effects

Severe neutropenia (rare) 1
Transient decreases in absolute lymphocyte counts 1
Action: Discontinue if neutrophil count ≤ 1,000 cells/mm³ 1

Autoimmune Exacerbation

May aggravate psoriasis 3, 4
Can cause subacute lupus-like syndrome 3, 4, 2

Depressive Symptoms

Have been reported during postmarketing surveillance 1
Action: Prescribers should be alert to depressive symptoms; patients should report them immediately 1

Drug Interactions

Terbinafine is an inhibitor of CYP450 2D6 isozyme and affects metabolism of:

Desipramine 1
Cimetidine 1
Fluconazole 1
Cyclosporine 1
Rifampin 1
Caffeine 1

Unlike azole antifungals, terbinafine has a relatively low potential for drug-drug interactions overall. 6, 7

Pregnancy and Lactation

The FDA label and guidelines do not provide specific recommendations for terbinafine use in pregnancy. Given the lack of safety data and the non-life-threatening nature of onychomycosis, systemic terbinafine should be avoided during pregnancy and deferred until after delivery. Topical therapy may be considered if treatment cannot be delayed.

Topical Terbinafine

Topical Formulations

Terbinafine 1% cream/gel: Applied once or twice daily for up to 2 weeks for tinea pedis, tinea corporis/cruris, cutaneous candidiasis, and pityriasis versicolor 7
Terbinafine 28% solution (film-forming solution): Applied twice daily for 6–12 months for superficial and distal onychomycosis 3

Efficacy

Achieves mycological cure in > 80% of patients with tinea pedis, tinea corporis/cruris, cutaneous candidiasis, and pityriasis versicolor when applied for up to 2 weeks 7
Topical agents alone are generally insufficient for pediatric fingernail onychomycosis; systemic therapy remains the preferred approach 4

Adverse Effects

Allergic contact dermatitis 3

Follow-Up and Monitoring

Clinical Reassessment

3–6 months after therapy initiation: Re-evaluate clinical response; consider additional treatment if disease persists 4, 2
48 weeks from treatment start: Monitor for at least this duration to detect possible relapses 4, 2

Expected Outcomes

Optimal clinical effect is seen some months after mycological cure and cessation of treatment, related to the period required for outgrowth of healthy nail 1
Nail terbinafine concentrations are detected within 1 week after starting therapy and persist for at least 30 weeks after completion of treatment 6

Prevention and Recurrence Reduction

To minimize reinfection and recurrence:

Decontaminate or replace contaminated footwear 4
Apply antifungal powders inside shoes regularly 4
Keep nails short and clean 4
Avoid sharing nail clippers with infected family members 4
Wear sandals or water shoes in public pools, locker rooms, and communal areas 4
Treat all infected family members simultaneously to lower recurrence risk 4

Emerging Resistance Considerations

Terbinafine resistance is increasingly reported, particularly in Trichophyton mentagrophytes and T. indotineae, due to SQLE gene mutations (most commonly Phe397Leu, Leu393Phe, Ala448Thr). 8, 9

Management of Suspected Resistance

Obtain detailed travel history, home and occupational exposure 8
Perform mycological examination (traditional and molecular) 8
MIC evaluation and SQLE mutation detection where available 8
If terbinafine resistance is suspected or confirmed, switch to itraconazole or voriconazole 8, 9
Intermittent itraconazole combined with antifungal local therapy is recommended for resistant cases 9
Expect recurrent courses and long-term therapy may be necessary 9

Special Populations

Patients with Diabetes

Terbinafine is preferred because of its low interaction profile; itraconazole is contraindicated when cardiac disease co-exists. 2

Immunosuppressed Individuals

Terbinafine and fluconazole are favored over itraconazole due to the high potential for interactions with antiretroviral agents. 2

Candida Onychomycosis

Terbinafine is less effective against Candida species; azole agents (itraconazole or fluconazole) are recommended for Candida-related nail infections. 2

Children

Children achieve higher cure rates and faster responses than adults because their nail plates are thinner (allowing better drug penetration) and their nails grow more rapidly (facilitating quicker clearance) 4
Terbinafine is unlicensed for pediatric use, requiring baseline LFTs and CBC before initiation 3, 4

Critical Pitfalls to Avoid

Do not start terbinafine without mycological confirmation to avoid treating non-fungal nail dystrophies 1, 2
Do not use terbinafine in patients with CrCl ≤ 50 mL/min; it is contraindicated, not dose-adjusted 5
Do not use terbinafine in active or chronic liver disease 1, 5, 2
Do not ignore patient-reported taste or smell disturbances; these can be permanent and require immediate discontinuation 1
Do not use griseofulvin as first-line therapy due to low efficacy (30–40% cure rate) 3, 4, 2
Do not forget to screen and treat all household members to prevent reinfection 4

What are the recommended dosing regimens, treatment durations, liver function monitoring, and contraindications for oral and topical terbinafine in dermatophyte infections, including onychomycosis, and its use in pregnancy?

Help us tailor your experience