SSRI-antipsychotic combination in psychotic depression: sertraline pharmacokinetics in the presence of olanzapine, a brief report from the STOP-PD study.

OBJECTIVE: We recently reported an unexpected interaction between olanzapine and sertraline in a population being treated for psychotic depression. Contrary to knowledge of cytochrome p450 interactions sertraline increased apparent clearance of olanzapine by 30%. Here we examined the pharmacokinetics of sertraline in the same population. Existing studies suggest that sertraline apparent clearance is significantly increased in male subjects and suggested an age/sex interaction. METHODS: We studied subjects undergoing combination of sertraline/olanzapine treatment for psychotic depression in the Study of the Pharmacotherapy of Psychotic Depression. Nonlinear mixed effect modelling software was used to examine the sertraline pharmacokinetics, evaluating age, sex, race, and olanzapine exposure as covariates. RESULTS: Eighty-seven subjects (median age 62 years, 28 male subjects, 11 African-Americans) provided 138 samples for sertraline concentration. Olanzapine exposure had a 14.8-fold range. A one compartment model with combined residual error described the sertraline concentration data adequately. Half-life and sex effect on sertraline apparent clearance (males averaging 50% higher (p < 0.005); 96.6 l/h vs 64.8 in female subjects) were similar to previous reports. No other covariate (age, race or olanzapine exposure) had a significant impact on apparent clearance, and no age/sex interaction emerged. CONCLUSION: Sertraline pharmacokinetics were similar to historical descriptions in populations not taking antipsychotics. Unlike our unexpected finding that sertraline increases olanzapine apparent clearance, olanzapine exposure had no impact on sertraline pharmacokinetics. Copyright © 2016 John Wiley & Sons, Ltd.

The Impact of Sertraline Co-Administration on the Pharmacokinetics of Olanzapine: A Population Pharmacokinetic Analysis of the STOP-PD.

BACKGROUND AND OBJECTIVE: Clinical evidence and expert opinion support using a combination of an antipsychotic and an antidepressant when treating major depression with psychotic features. We characterized the impact of sertraline co-administration on olanzapine clearance in psychotic depression using population pharmacokinetic methods. METHODS: The Study of Pharmacotherapy for Psychotic Depression (STOP-PD) randomized 259 participants to olanzapine plus placebo or olanzapine plus sertraline. Olanzapine was started at 2.5-5 mg/day and sertraline at 25-50 mg/day. Doses were increased to a maximum of 20 mg/day for olanzapine and 200 mg/day for sertraline. Up to four olanzapine concentration samples were collected during the 12-week trial and 12-week continuation phase. We used NONMEM (Version VII) for population pharmacokinetic analysis, assessing effects of the covariates sex, African American origin, smoking, age, and sertraline co-administration. RESULTS: Population pharmacokinetic analysis comprised 336 samples from 175 individuals. The structural model published by Bigos et al. was sufficient to describe the olanzapine data adequately: a one-compartment model with first-order absorption and elimination, using an additive residual error structure with the absorption rate constant fixed to 0.5. Sertraline co-administration significantly increased olanzapine apparent clearance (p < 0.005) by 25-35 % depending on the patient characteristics included. Male sex was associated with a significantly increased clearance. Age and race did not have a significant impact on clearance. CONCLUSIONS: Contrary to expectations from the knowledge of cytochrome P450 interactions, sertraline increased olanzapine apparent clearance. Plausible explanations include patients treated with sertraline having poorer adherence to olanzapine, or the impact of sertraline inhibition of transporters resulting in increased intracellular concentrations and thus access to metabolizing enzymes.