Which of the following antifungal drugs is contraindicated in patients with baseline hepatic impairment due to its hepatotoxicity and extensive hepatic metabolism?

Explanation

## Hepatotoxicity Profile of Antifungals **Key Point:** Terbinafine is an allylamine antifungal with significant hepatotoxic potential. It undergoes extensive hepatic metabolism (CYP2D6, CYP3A4) and can cause idiosyncratic liver injury, including fulminant hepatic failure in rare cases. ## Antifungal Hepatotoxicity Comparison | Drug | Hepatotoxicity Risk | Metabolism | Clinical Implication | |---|---|---|---| | **Terbinafine** | **High (idiosyncratic)** | **Extensive hepatic** | **Contraindicated in liver disease** | | Amphotericin B | Low (renal toxicity > hepatic) | Minimal hepatic | Safer in liver disease | | Caspofungin | Minimal | Hepatic inactivation (not CYP) | Safe; dose adjustment in severe cirrhosis | | Fluconazole | Low-moderate | Hepatic (CYP3A4) | Caution; monitor LFTs | **High-Yield:** Terbinafine requires baseline LFTs and periodic monitoring. It is absolutely contraindicated in patients with pre-existing cirrhosis or chronic hepatitis. **Warning:** Terbinafine-induced liver injury can occur weeks to months after initiation and may not be dose-dependent (idiosyncratic reaction). **Clinical Pearl:** Terbinafine is preferred for onychomycosis (nail fungal infections) in patients with normal liver function because of its superior efficacy and shorter treatment duration (12 weeks vs. 6–12 months for itraconazole). However, liver disease shifts the risk–benefit ratio unfavorably. ## Mechanism of Terbinafine Hepatotoxicity Terbinafine is metabolized by hepatic cytochrome P450 enzymes into multiple metabolites, some of which may form reactive intermediates that cause hepatocellular injury through immune-mediated or direct toxic mechanisms.