Relationship between Patients' Clinical Background and Lithium Concentration in Plasma: An Analysis of TDM Database in a University Hospital in Japan.

Abstract

The purpose of the present study was to clarify the relationship between Japanese patients' clinical background and the lithium concentration in plasma. We extracted patient data for 4 years from our database (April 1, 1993 through March 30, 1997) in the Clinical Pharmacology Center of Oita Medical University Hospital, under the conditions that 1) the patient's body weight, sex and age were known, 2) the patient's lithium concentration in plasma was confirmed to be in steady state at more than 30 days after initial drug administration, and 3) the sample was taken at trough level at exactly 12 hours after the previous drug intake. Sixty-four out of 752 samples met the criteria. The ratios of the lithium concentration in plasma to the dose per kilogram body weight (C/ D ratio) were compared according to the patients' background factors ; 1) in/outpatient status and 2) age. The mean C/D ratio of inpatients was higher than that of outpatients. The C/D ratio increased with age, and it tended to increase more in inpatients. The correlation of the concentration to the dose was higher with the higher age. We propose by analyzing the patients' C/D ratios, that the patient's clinical background correlates with the patient's drug compliance, or pharmacokinetics. The C/D ratio may be a useful indicator to evaluate the patient's drug compliance and pharmacokinetics in daily bedside therapeutic drug monitoring.