Reactions 688 - 14 Feb 1998

Clozapine interacts withfluvoxamine

The addition of fluvoxamine, but not paroxetine, toclozapine treatment regimens resulted in a significantincrease in serum concentrations of clozapine and itsmetabolites, report researchers from Germany.

In the study, 20 men and 10 women withschizophrenia received clozapine 2.5–3 mg/kg/day; 16of these patients then received fluvoxamine 50 mg/dayand the other 14 patients received paroxetine 20mg/day. Seven and 14 days later, recipients of clozapineand fluvoxamine showed an approximate 3-fold increasein their serum concentrations of clozapine, N-desmethylclozapine and clozapine-N-oxide. However,the addition of paroxetine to clozapine, did not result insignificant changes in concentrations of clozapine or itsmetabolites.

These effects were probably the result of inhibition byfluvoxamine of the enzymes catalysing the degradationof clozapine and N-desmethylclozapine. Thus, dosealterations will be required in patients treated withclozapine and fluvoxamine, say the researchers.Wetzel H, et al. Pharmacokinetic interactions of clozapine with selective serotoninreuptake inhibitors: differential effects of fluvoxamine and paroxetine in aprospective study. Journal of Clinical Psychopharmacology 18: 2-9, Feb1998 800638029

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Reactions 14 Feb 1998 No. 6880114-9954/10/0688-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved