Objective: To conduct a systematic review examining the relationships between olanzapine dose, clinical outcome, dopamine occupancy, and plasma concentration; and to evaluate the potential for therapeutic drug monitoring.
Methods: A search using Embase, Medline, and Pubmed was conducted; and the literature was systematically reviewed. Studies meeting inclusion criteria were examined. The relationships between olanzapine dose, response, dopamine occupancy, and concentration were analyzed using statistical regression.
Results: Ten studies were included in the analysis for dose-response. The effect size-dose relationship showed a typical dose-response curve with minimal rise in slope for doses higher than 10 mg/d. For the dose-occupancy relationship, 6 studies were included. Doses more than approximately 12 mg/d were sufficient to block 65% of striatal D2 receptors. Doses higher than 20 mg led to minimally higher receptor occupancies. Fifteen studies were included in the meta-regression of olanzapine mean concentrations. A linear relationship between mean plasma concentration and mean dose was observed.
Conclusions: Our review suggests that the likelihood of a favorable response with olanzapine is maximized at doses of 10 to 15 mg/d (perhaps lower in nonsmoking females). Higher doses may be considered if 15 mg is ineffective and if plasma level is less than 20 ng/mL on that dose. There is a direct linear relationship between olanzapine dose and plasma concentration. Therapeutic drug monitoring may be useful in patients who are suspected of nonadherence, where there is potential for a drug interaction, and in patients taking 15 mg/d or more and who have not reached clinical response.