Olanzapine pharmacokinetics in pediatric and adolescent inpatients with childhood-onset schizophrenia

Well-designed studies investigating how pediatric or adolescent patients wi th mental disorders respond to and metabolize the newer antipsychotic drugs are practically nonexistent. Without such data, clinicians have difficulty designing appropriate dosage regimens for patients in these age groups. Th e results from a study of olanzapine pharmacokinetics in children and adole scents are described. Eight inpatients (ages 10-18 years) with treatment-re sistant childhood-onset schizophrenia received olanzapine (2.5-20 mg/day) o ver 8 weeks. Blood samples, collected during dose titration and at a steady state provided pharmacokinetic data. The final evaluation (week 8) include d extensive sampling for 36 hours after a 20-mg dose. Olanzapine concentrat ions in these eight pediatric patients were of the same magnitude as those for nonsmoking adult patients with schizophrenia but may be as much as twic e the typical olanzapine concentrations in patients with Schizophrenia who smoke. Olanzapine pharmacokinetic evaluation gave an apparent mean oral cle arance of 9.6 +/- 2.4 L/hr and a mean elimination half-life of 37.2 +/- 5.1 hours in these young patients. The determination of the initial olanzapine dose for adolescent patients should take into consideration factors such a s the patient's size. In general, however, the usual dose recommendation of 5 to 10 mg once daily with a target: dose of 10 mg/day is Likely a good cl inical guideline for most adolescent patients on the basis of our pharmacok inetics results.