Factors Affecting Chlorpromazine Plasma Levels in Psychiatric Patients

IT RECENTLY became possible to Measure concentrations of chlorpromazine and some of its relatively nonpolar metabolites in the plasma of psychiatric patients.1As a result chlorpromazine, the demethylated analogues of chlorpromazine, and chlorpromazine sulfoxide, were identified unequivocably for the first time in human plasma.2-4These preliminary studies showed considerable interpatient and intrapatient variation in plasma levels of these materials in subjects on similar chlorpromazine dosage regimens. The clinical significance of this finding is that certain patients may have a poor response to medication because of variations in rates of absorption and metabolism, resulting in unusually high or low plasma and tissue levels. The present report describes an investigation of some of the factors which modify plasma levels of chlorpromazine. Methods Plasma samples were collected in a disposable aspirating syringe (Vacutainer tubes, B-D Products), containing potassium oxalate, from acutel" and