Abstract
Introduction Therapeutic drug monitoring is necessary for lithium, but clinical application of
several prediction strategies is still limited because of insufficient predictive
accuracy. We herein proposed a suitable model, using creatinine clearance (CLcr)-based
lithium clearance (Li-CL).
Methods Patients receiving lithium provided the following information: serum lithium and
creatinine concentrations, time of blood draw, dosing regimen, concomitant medications,
and demographics. Li-CL was calculated as a daily dose per trough concentration for
each subject, and the mean of Li-CL/CLcr was used to estimate Li-CL for another 30
subjects. Serum lithium concentrations at the time of sampling were estimated by 1-compartment
model with Li-CL, fixed distribution volume (0.79 L/kg), and absorption rate (1.5/hour)
in the 30 subjects.
Results One hundred thirty-one samples from 82 subjects (44 men; mean±standard deviation
age: 51.4±16.0 years; body weight: 64.6±13.8 kg; serum creatinine: 0.78±0.20 mg/dL;
dose of lithium: 680.2±289.1 mg/day) were used to develop the pharmacokinetic model.
The mean±standard deviation (95% confidence interval) of absolute error was 0.13±0.09
(0.10–0.16) mEq/L.
Discussion Serum concentrations of lithium can be predicted from oral dosage with high precision,
using our prediction model.
Key words
lithium - prediction - therapeutic drug monitoring
