Olanzapine serum concentrations in psychiatric patients given standard doses: the influence of comedication.
We recorded steady state serum concentrations of olanzapine in 56 psychiatric patients under routine conditions. Twenty-two patients (39%) underwent monotherapy; the rest received additional psychotropic drugs. Doses were given once daily in the evening, and serum olanzapine levels were measured 12 hours later. For the whole group, the concentration-to-dose ratio (C/D) varied 26-fold, with a median value of 4.8 (nmol/L)/(mg/24 hours), but 80% of the patients had C/D values within the range 2 to 10 (nmol/L)/(mg/24 hours). All but three patients received standard doses (5-20 mg/24 hours), of whom 80% had serum concentrations of olanzapine within the range 22 to 146 nmol/L. Patients comedicated with potential inhibitors of CYP2D6 and other drugs displayed a median C/D approximately 40% higher than the group undergoing monotherapy. Patients comedicated with carbamazepine had a median C/D 36% lower than that of the monotherapy group. Therefore, the serum concentration range (12-hour values) of 25 to 150 nmol/L can be expected for patients receiving a standard daily dose.
Institute for Basic Psychiatric Research, Department of Biological Psychiatry, Psychiatric Hospital in Aarhus, Aarhus University Hospital, Risskov, Denmark.
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D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000097:blood* / Q000493:pharmacokinetics; D001569:Benzodiazepines; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004347:Drug Interactions; D016903:Drug Monitoring; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077152:Olanzapine; D010890:Pirenzepine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D011618:Psychotic Disorders / Q000097:blood* / Q000378:metabolism
D014150:Antipsychotic Agents; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004791:Enzyme Inhibitors; D001569:Benzodiazepines; D010890:Pirenzepine; D000077152:Olanzapine