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 studied 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 estimated at 0.84 +/- 0.32 l/kg and renal clearance was 0.38 +/- 0.11 ml/mn/kg. After chronic intoxication lithium pharmacokinetics differed from those 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. These modifications in lithium elimination kinetics could be related to the decrease in the glomerular filtration rate with age or renal dysfunction in this group of patients.