Can a 34-year-old woman with a glomerular filtration rate of 116 mL/min/1.73 m² and elevated aspartate aminotransferase (113 U/L) and alanine aminotransferase (261 U/L) safely take oral terbinafine?

No, oral terbinafine should NOT be prescribed to this patient due to significantly elevated liver transaminases

This 34-year-old woman with ALT 261 U/L (approximately 6.5× upper limit of normal) and AST 113 U/L (approximately 2.8× upper limit of normal) has a clear contraindication to terbinafine therapy, as systemic terbinafine is not recommended in patients with active or chronic liver disease. 1

Why Terbinafine is Contraindicated

Pre-existing Liver Disease Exclusion

• The British Association of Dermatologists explicitly states that systemic terbinafine is not recommended in patients with active or chronic liver disease 1
• Baseline liver function tests are recommended before initiating terbinafine specifically to identify patients like this one who should not receive the drug 1
• Although terbinafine is associated with only minimal hepatic toxicity in healthy patients, rare reports of serious hepatotoxicity have occurred, usually in patients with pre-existing liver disease 1

Severity of Transaminase Elevation

• This patient's ALT of 261 U/L represents a >3× upper limit of normal elevation, which is the threshold used to define clinically significant hepatotoxicity 1
• Her transaminase pattern (ALT >> AST) suggests active hepatocellular injury, not just chronic stable liver disease 1
• Even in patients already on terbinafine, the drug should be held when ALT rises to ≥3× ULN 1

Renal Function is NOT the Issue

• Her GFR of 116 mL/min/1.73 m² is normal to high-normal and poses no contraindication 1
• Terbinafine clearance is decreased only in patients with severe kidney disease, not at this GFR level 1
• More than 99% of terbinafine is cleared by the kidney, but dose adjustment is not needed until severe renal impairment is present 1

Clinical Reasoning Algorithm

Step 1: Check baseline liver function → This patient has ALT >6× ULN
Step 2: Determine if liver disease is active → Yes, significantly elevated transaminases indicate active hepatocellular injury
Step 3: Apply contraindication → Do not prescribe terbinafine 1

What Should Be Done Instead

Immediate Actions

• Investigate the cause of her elevated transaminases before treating any fungal infection 1
• Evaluate for viral hepatitis, autoimmune hepatitis, medication-induced liver injury, alcohol use, non-alcoholic fatty liver disease, and other hepatobiliary pathology
• Repeat liver function tests in 48-72 hours to assess trajectory 1

Alternative Antifungal Options (Once Liver Status Clarified)

• Topical antifungals (ciclopirox, amorolfine) can be used for onychomycosis without systemic absorption concerns 1
• Griseofulvin may be considered if oral therapy is absolutely necessary, though it also requires baseline liver monitoring and is less effective than terbinafine 1
• Itraconazole is an alternative oral agent but also carries hepatotoxicity risk and would require the same caution in this patient 1

Common Pitfalls to Avoid

• Do not assume normal renal function makes terbinafine safe — the contraindication here is hepatic, not renal 1
• Do not start terbinafine with a plan to "monitor closely" — the drug should not be initiated in the presence of active liver disease 1
• Do not overlook that onychomycosis is not life-threatening — delaying treatment until liver function normalizes is appropriate 1
• Do not forget that terbinafine-induced hepatotoxicity can be severe — cases of cholestatic hepatitis requiring 11-15 months for resolution have been reported 2

Risk Context from the Literature

• Post-marketing surveillance shows serious adverse events occur in only 0.04% of terbinafine users 1
• However, when hepatotoxicity does occur, it can be severe and prolonged, with peak bilirubin reaching 718 μmol/L and recovery taking over a year 2
• Most hepatotoxicity occurs in patients with pre-existing liver disease, making this patient particularly high-risk 1