Small molecule
PubChem CID 1549008
Terbinafine
Lamisil
- Mechanism of action
- Inhibits fungal squalene epoxidase, blocking ergosterol synthesis
- In plain language
- Blocks an enzyme fungi need to build their cell membrane, causing a toxic buildup that kills the fungal cell.
- How it works
- Terbinafine is an allylamine antifungal that inhibits squalene epoxidase, the enzyme that converts squalene to lanosterol in the early steps of ergosterol biosynthesis, a sterol essential to the fungal cell membrane. This blockade causes accumulation of squalene within the fungal cell, and the resulting increase in membrane permeability — rather than the ergosterol deficiency itself — is believed to be the primary driver of fungal cell death. Depending on drug concentration and the fungal species tested in vitro, terbinafine hydrochloride may be fungicidal, though the manufacturer's label notes the clinical significance of these in vitro susceptibility data is unknown. Terbinafine distributes into sebum and skin, with a terminal half-life of 200-400 hours reflecting slow elimination from tissues like skin and adipose, which underlies its use against dermatophyte infections of the nail.
- Therapeutic applications
- Terbinafine tablets are indicated for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes (tinea unguium). Diagnosis should be confirmed prior to treatment with appropriate nail specimen testing, such as potassium hydroxide (KOH) preparation, fungal culture, or nail biopsy. Dosing is one 250 mg tablet once daily for 6 weeks for fingernail infections and 12 weeks for toenail infections, and the label notes optimal clinical improvement is typically seen months after mycological cure, related to the time needed for healthy nail to grow out. In vitro, terbinafine also shows activity against Candida albicans and other organisms, though the label states safety and efficacy for treating clinical infections due to these organisms have not been established in adequate, well-controlled trials.
- Class
- Small molecule
- Therapeutic area
- Antifungal
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