PHARMACOKINETICS OF LITHIUM IN PLASMA AND RED-BLOOD-CELLS IN ACUTE AND CHRONIC INTOXICATED PATIENTS

Lithium disposition in plasma, red blood cells (RBC) and urine was stu died in acute self-poisoned patients upon chronic lithium therapy (n = 4) and in chronic intoxicated patients receiving oral lithium (n = 10 ). Following acute intoxication upon chronic lithium therapy, lithium pharmacokinetics did not differ from previous reports. Terminal plasma half-life ranged from 19.0 - 29.0 h and RBC/plasma ratio was 0.32 +/- 0.11. The distribution volume of the terminal phase, Vz, was estimate d at 0.84 +/- 0.32 l/kg and renal. clearance was 0.38 +/- 0.11 ml/mn/k g. After chronic intoxication lithium pharmacokinetics differed from t hose of the acute patients. Terminal plasma half-life ranged from 36.5 - 79.4 h and zero-order decline appeared in 8 of the 10 patients. The RBC/plasma ratio was 0.87 +/- 0.22 on admission. Vz was estimated at 0.71 +/- 0.27 l/kg and renal clearance was 0.16 +/- 0.07 ml/mn/kg. The se modifications in lithium elimination kinetics could be related to t he decrease in the glomerular filtration rate with age or renal dysfun ction in this group of patients.