CITALOPRAM CAUSES NO SIGNIFICANT ALTERATIONS IN PLASMA NEUROLEPTIC LEVELS IN SCHIZOPHRENIC-PATIENTS

Steady-state plasma concentrations of commonly used neuroleptic drugs were measured in 90 schizophrenic patients before and after adding pla cebo or citalopram (40 mg/day) to their treatment regimen. Plasma conc entrations of citalopram and its main metabolite, desmethylcitalopram, were also measured. In addition, patients with exceptionally high neu roleptic levels or an increase in adverse effects during the 12-week s tudy period were evaluated for their debrisoquine/sparteine hydroxylas e (CYP2D6) genotype, an enzyme responsible for oxidative metabolism of several neuroleptics and selective serotonin re-uptake inhibitors. Th ere were no significant changes in plasma concentrations of haloperido l, chlorpromazine, zuclopenthixol, levomepromazine, thioridazine or pe rphenazine during the study. Plasma concentrations of citalopram and d esmethylcitalopram were well within the levels reported previously wit h monotherapy, and remained stable throughout the study. None of the 1 5 patients analysed for the CYP2D6 genotype was a poor metabolizer. It is concluded that clinically important pharmacokinetic drug interacti ons do not play a crucial role when citalopram is used as an augmentat ion therapy in neuroleptic-treated schizophrenic patients.