Population pharmacokinetics of risperidone and 9-hydroxyrisperidone in patients with acute episodes associated with bipolar I disorder

A population model was developed with the aim to simultaneously describe risperidone and 9-hydroxyrisperidone pharmacokinetics; to obtain estimates for pharmacokinetic parameters and associated inter- and intra-individual variability of risperidone and 9-hydroxyrisperidone; and to evaluate the influence of patient demographic characteristics and other factors on risperidone, 9-hydroxyrisperidone, and active moiety pharmacokinetics. Data were obtained from 407 patients enrolled in four Phase 1 (serial blood sampling) and three Phase 3 trials (sparse sampling), representing dosage regimens ranging from 4 mg single dose to flexible 1-6 mg once daily. A pharmacokinetic model with two-compartment submodels for risperidone and 9-hydroxyrisperidone disposition and a sequential zero- and first-order absorption pathway was selected based on prior knowledge. A mixture model was incorporated due to CYP2D6 polymorphism of risperidone conversion to 9-hydroxyrisperidone. Patient characteristics tested as potential covariates were: age, sex, race, body weight, lean body mass, body mass index, creatinine clearance, liver function laboratory parameters, study, and carbamazepine comedication. The quasi-clearance of active moiety (the sum of risperidone and 9-hydroxyrisperidone) was simulated and linear regression performed to identify significant covariates. The selected pharmacokinetic model described the plasma concentration-time profiles for risperidone and 9-hydroxyrisperidone quite well and was able to determine each patient's phenotype. Covariates significantly affecting the pharmacokinetics were carbamazepine comedication, and study because the proportion of patients assigned to the intermediate metabolizer status decreased from single to multiple dosing while the proportion assigned to extensive metabolizer status increased. Covariates with limited and clinically irrelevant effects on active moiety concentrations were patient phenotype, race, and total protein. Carbamazepine also decreased active moiety concentrations

Modeling the effectiveness of paliperidone ER and olanzapine in schizophrenia: meta-analysis of 3 randomized, controlled clinical trials

The time course of Positive and Negative Syndrome Scale (PANSS) scores in adult schizophrenia patients was modeled, and the effectiveness of paliperidone extended-release tablets (paliperidone ER) and olanzapine was quantified. Data from 3 randomized, double-blind phase III studies were used. Patients received paliperidone ER (3, 6, 9, 12, or 15 mg), olanzapine 10 mg, or matched placebo once daily for 6 consecutive weeks. An indirect response model implemented using a nonlinear mixed effects approach described the time course of the PANSS. Deterioration rate was modeled as a function of baseline PANSS score, placebo, and drug effects, and the dropout effect. An exponential decrease of the placebo response was also implemented. Paliperidone ER and olanzapine treatment were characterized by a long-lasting drug effect (13%), with a larger but short-lasting placebo effect (40%) and a notable dropout rate. The covariate exploration failed to identify any clinically relevant factors. The non-parametric bootstrap analysis confirmed the acceptable precision of parameter estimates. The visual predictive check supported the model's adequacy to reproduce observed PANSS time courses. The population model describes the time course of PANSS scores in schizophrenia patients and is appropriate for use in clinical trial simulation activities