Effects of adjunctive fluvoxamine on metabolic parameters and psychopathology in clozapine-treated patients with schizophrenia: A 12-week, randomized, double-blind, placebo-controlled study

Objective: Numerous studies have demonstrated that fluvoxamine has considerable pharmacokinetic and pharmacodynamic interactions with clozapine. We conducted a 12-week, randomized, double-blind, placebo-controlled study to evaluate the effects of fluvoxamine on metabolic parameters and psychopathology in clozapine-treated patients with schizophrenia. Methods: We recruited 85 patients who received a DSM-IV diagnosis of schizophrenia. Eligible patients were randomized to receive fluvoxamine 50. mg/day plus clozapine 100. mg/day or clozapine 300. mg/day. We studied metabolic parameters, psychopathology, and drug levels at baseline and 4, 8, and 12. weeks after the intervention. Plasma levels of clozapine, norclozapine, clozapine N-oxide, and fluvoxamine were determined using high-performance liquid chromatography with ultraviolet detection. Results: No significant difference was observed in baseline characteristics between the two groups. Clozapine-fluvoxamine combined treatment significantly attenuated the increments in body weight, insulin resistance, and levels of insulin, glucose, and triglycerides compared with clozapine monotherapy. Both groups exhibited significant improvements in their Positive and Negative Syndrome Scale (PANSS) total and negative scores. The combined treatment group showed significant reduction in the PANSS general psychopathology scores compared with the monotherapy group. No difference was observed in the plasma clozapine level between the two groups. The monotherapy group showed higher levels of norclozapine and clozapine N-oxide than the combined group. Conclusions: Compared with clozapine monotherapy, treatment with adjunctive fluvoxamine with clozapine for 12. weeks can alleviate body weight gain and metabolic abnormalities in patients with schizophrenia, without sacrificing the clinical effect. Clinicians should interpret these findings cautiously considering the short duration of this study.The study was registered at www.clinicaltrials.gov (NCT01401491).