[Addition of fluvoxamine to clozapine: theory and practice].

BACKGROUND: The addition of fluvoxamine to clozapine induces a rise of plasma concentrations of clozapine. This enables the prescription of a lower number of clozapine tablets, yet it attains sufficient clozapine plasma concentrations, and facilitates treatment adherence. AIM: Providing practical advice for the practical implementation of the addition of fluvoxamine to clozapine. METHOD: A review of the literature with Ovid Medline and the presentation of a case series (N=7). RESULTS: Addition of 25 or 50 mg fluvoxamine induces a mean rise of plasma concentrations of clozapine with a factor 2-3, probably even higher with the addition of 100 mg. However, the range of this factor varies considerably between individuals. The use of clozapine and fluvoxamine at the same time possibly has a favourable impact on the metabolic side-effects of clozapine. CONCLUSION: Addition of fluvoxamine to clozapine can lead to a dangerous rise of clozapine plasma concentrations. However, it can also be used to prescribe a lower number of clozapine tablets and to facilitate treatment adherence. A sufficient safety margin should be taken and regular control of clozapine plasma concentrations is mandatory.