Clinical Research Directory

Inclusion Criteria: * Standard treatment of a stable, oral dose of clozapine for at least one week (at steady state). * Age between 18-70 years. * Registered time of intake as well as sampling time and dosage. * Registered smoking status (yes/no). * At least two samples in the elimination phase of clozapine with both clozapine and norclozapine measured. * Measurement of the white cell count at least every three months or more often. * Routine metabolic screening performed at moment of inclusion. * Subjects should be able to understand the study information and procedures and give informed consent or when incapacitated subjects are not reliably able to give informed consent their legal representatives should give informed consent under the condition that these subjects are willing to participate. Exclusion Criteria: * Pregnancy. * Malignancy or treatment with immunosuppressive medication. * Samples where cessation, start or dose change of interacting co-medication (such as valproic acid, gemfibrozil, fluvoxamine, omeprazole and cyclic oral contraceptives \[21 on, 7 days off\]) or changes in use of tobacco containing products occurred within seven days prior to blood sampling (21, 28, 34, 35). * Acute inflammation, infection or samples shortly after intoxication. In case this information is unknown, it may be derived by large unexpected change in levels compared to previous or target levels. * Not sampled at Starlet (blood collection site) or sampled by dried blood spot * Unknown status of smoking (including vaping). * Unknown time of intake of clozapine. * Unknown time of blood sampling. * If informed consent is not obtained by the patient or by a legal representative in a mentally incapacitated patient, i.e. a legally incompetent adult.