In vitro studies with human liver microsomes showed that terbinafine does not inhibit the
metabolism of tolbutamide, ethinylestradiol, ethoxycoumarin, and cyclosporine. In vitro studies have also
shown that terbinafine inhibits CYP2D6-mediated metabolism. This may be of clinical relevance for compounds
predominantly metabolized by this enzyme, such as tricyclic antidepressants, ß-blockers, selective serotonin
reuptake inhibitors (SSRIs), and monoamine oxidase inhibitors (MAO-Is) Type B, if they have a narrow therapeutic
In vivo drug-drug interaction studies conducted in normal volunteer subjects showed that
terbinafine does not affect the clearance of antipyrine or digoxin. Lamisil decreases the clearance of caffeine
by 19%. Lamisil increases the clearance of cyclosporine by 15%.
There have been spontaneous reports of increase or decrease in prothrombin times in patients
concomitantly taking oral terbinafine and warfarin, however, a causal relationship between LAMISIL®
Tablets and these changes has not been established.
Lamisil clearance is increased 100% by rifampin, a CyP450 enzyme inducer, and decreased 33% by
cimetidine, a CyP450 enzyme inhibitor. Lamisil clearance is unaffected by cyclosporine.
There is no information available from adequate drug-drug interaction studies with the following
classes of drugs: oral contraceptives, hormone replacement therapies, hypoglycemics, theophyllines, phenytoins,
thiazide diuretics, beta blockers, and calcium channel blockers.