Schizophrenia is a chronic illness with a progressive course that can be marked by resistance to antipsychotic treatment. This can make therapeutic support challenging for the practitioner, with results that are partial and unsatisfactory. In the literature, treatment with high-dose olanzapine (>20mg/day) appears to be a good alternative to clozapine, the gold standard for treatment-resistant schizophrenia. In the present observational prospective study, we studied the clinical and biological profiles of patients treated with olanzapine doses up to 100mg/day. In total, 50 patients were clinically and biologically assessed. We found a linear relationship between oral dose and serum concentration (Pearson's r=0.83, p<0.001) with effects of tobacco (p<0.05) and of coffee and tea consumption (p<0.01). Tolerance seemed to be good regardless of dose. No link was found between concentration and efficiency. Despite a nonexhaustive assessment of pharmacokinetic parameters, not least pharmacogenetic data (e.g., genotyping of cytochrome P450-1A2 or glycoprotein P Abcb1a), pharmacokinetic aspects alone cannot account for why the disease may sometimes be resistant to 20mg of olanzapine but respond to higher doses. A nuclear imaging study exploring brain occupancy by high-dose olanzapine, coupled with the abovementioned pharmacokinetic assessment, may prove a relevant experimental paradigm for studying the pathophysiological mechanisms of resistant schizophrenia.
Keywords: High dose; Olanzapine; Schizophrenia; Therapeutic drug monitoring; Therapeutic resistance.
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