Terbinafine Hydrochloride

As a CYP2C9 and CYP3A4 inhibitor, likely to substantially increase terbinafine systemic exposure similar to fluconazole.

Terbinafine decreases caffeine clearance by 19%, potentially increasing caffeine exposure.

Cimetidine decreases terbinafine clearance by 33%, potentially increasing terbinafine exposure.

Terbinafine increases cyclosporine clearance by 15%, potentially decreasing cyclosporine exposure. Monitoring recommended.

Terbinafine inhibits CYP450 2D6 metabolism, resulting in 2-fold increase in Cmax and 5-fold increase in AUC. Effects persist for 4 weeks after discontinuation. Careful monitoring and dose reduction may be required.

Terbinafine increases dextromethorphan/dextrorphan metabolite ratio by 16- to 97-fold, converting extensive metabolizers to poor metabolizer status. Careful monitoring and dose reduction may be required.

Terbinafine inhibits CYP450 2D6, the primary metabolic pathway for flecainide. Careful monitoring and dose reduction may be required.

Fluconazole increases terbinafine Cmax by 52% and AUC by 69%. Fluconazole inhibits CYP2C9 and CYP3A enzymes affecting terbinafine metabolism.

As a CYP2C9 and CYP3A4 inhibitor, likely to substantially increase terbinafine systemic exposure similar to fluconazole.

Terbinafine inhibits CYP450 2D6, the primary metabolic pathway for propafenone. Careful monitoring and dose reduction may be required.

Rifampin increases terbinafine clearance by 100%, substantially reducing terbinafine exposure. Dose adjustment may be necessary.

Spontaneous reports of increased or decreased prothrombin times with concomitant oral terbinafine and warfarin, though causal relationship not established.

The influence of terbinafine on the pharmacokinetics of fluconazole, cotrimoxazole (trimethoprim and sulfamethoxazole), zidovudine or theophylline was not considered to be clinically significant.

In vitro studies with human liver microsomes showed that terbinafine does not inhibit the metabolism of tolbutamide, ethinylestradiol, ethoxycoumarin, cyclosporine, cisapride and fluvastatin.

The influence of terbinafine on the pharmacokinetics of fluconazole, cotrimoxazole (trimethoprim and sulfamethoxazole), zidovudine or theophylline was not considered to be clinically significant.

In vitro studies with human liver microsomes showed that terbinafine does not inhibit the metabolism of tolbutamide, ethinylestradiol, ethoxycoumarin, cyclosporine, cisapride and fluvastatin.