Terbinafine achieves mycological cure in onychomycosis better than older agents because its target lies early in ergosterol synthesis. Its mechanism of action is inhibition of:

• A Squalene epoxidase ✓
• B 14-alpha-demethylase
• C Beta-1,3-glucan synthase
• D Thymidylate synthetase

Explanation

Terbinafine is an allylamine that inhibits fungal squalene epoxidase, blocking conversion of squalene to lanosterol at the first committed step of ergosterol biosynthesis. Accumulated squalene is toxic to the fungus, giving fungicidal activity against dermatophytes. Azoles act later in the pathway at 14-alpha-demethylase, and echinocandins act on glucan synthase, so those options describe entirely different drug classes. Its oral use with monitoring relates to hepatotoxicity, not the target itself.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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