Fluvoxamine increases the clozapine serum levels significantly.

In this case report we describe an interaction between clozapine and fluvoxamine in two physically healthy patients meeting the DSM-IIIR criteria for paranoid schizophrenia. The substantial rise of clozapine serum levels suggest that caution should be exercised when combining fluvoxamine with clozapine as the clozapine concentration may increase by a factor of 5-10.