In vitro studies using human liver microsomes show no or little (< 25%) inhibition of cytochrome P450 isozymes 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1 or 3A4 at zonisamide levels approximately two- fold or greater than clinically relevant unbound serum concentrations.