Olanzapine plasma concentration ≥ 23, 2 ng/ml have been identified as a predictor of clinical response in acutely ill patients with schizophrenia. Aim was to determine relation between plasma concentration of olanzapine in a sample of inpatients or outpatients with acute mania by defining a plasma threshold (above which a better clinical response was obtained).

Open label, longitudinal, multicentric study including patients with acute mania and treated by olanzapine for 6 weeks; plasma concentration of olanzapine was measured at 3 and 6 weeks by high-performance liquid chromatography. Patients were considered “responsive” if they showed at least a 50% reduction in Young Mania Rating Scale score and a Clinical Global Impression Severity scale score of ≤ 3.

Twenty patients were including (13 men and 7 women), mean age 57.4 yr. The mean olanzapine dosage was 11.46 mg/day (SD=2.49) at the same dosage for 16.8 days (SD=6.5). Receiver operating characteristic curve analysis determined a plasma threshold to be 15, 9 ng/ml.

It's the first time that a threshold of Olanzapine is determined in bipolar mania into a consequent population. This result could be considered as additional tools to adjust posology for improve cares, when manic patients are resistant.