Terbinafine hydrochloride (KWD 2019) is a synthetic allylamine derivative structurally related to naftifine. Terbinafine is active against dermatophytes.

Terbinafine (50 μM to 100 μM) inhibits only marginally the metabolism of ethoxycoumarin (CYP1A2), tolbutamide (CYP2C9), or ethynylestradiol, CsA, and cortisol. Terbinafine proves to be a potent inhibitor of the CYP2D6-mediated dextromethorphan O-demethylation and bufuralol 1-hydroxylation with IC50values of 0.2 μM and 0.25 μM, respectively. [1] Terbinafine is highly activ Aspergillus isolates (minimum inhibitory concentration [MIC] 0.01 to 2 mg/mL) with a primary fungicidal action (minimum fungicidal concentration [MFC] 0.02 to 4 mg/mL). [2] Terbinafine inhibits dextromethorphan O-demethylation with an apparent Ki ranging from 28 to 44 nM in human hepatic microsomes and averaging 22.4 nM for the heterologously expressed enzymes. [3] Terbinafine shows a very strong activity in vitro against Penicillium spp., Paecilomyces spp., Trichoderma spp., Acremonium spp. and Arthrographis spp. with GMs <1 mg/L. [4] Terbinafine decreases the levels of phosphorylated extracellular signal-regulated kinase (ERK). Terbinafine might cause a decrease of MEK, which in turn up-regulates p53 through the inhibition of ERK phosphorylation, and finally causes an increase of p21expression and cell-cycle arrest. [5]

Terbinafine demonstrates efficacy both as a topical application and through oral administration in experimental dermatophytoses. Notably, in guinea pigs infected with fungi, a significant decrease in skin temperature is observed after the fourth terbinafine treatment[6].