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Twenty-two patients, 8 males and 14 females, who had been lithium-free for at least 1 week were included in this study. All patients took 900 mg of Lithonate at 8:00 a.m. while in a fasting state. A 5 ml blood sample was taken at 9:00 a.m., 10 a.m., 12 noon, 3 p.m., 5 p.m., 11 p.m., and at 9 a.m. and 3 p.m. on the next day. Plasma was separated immediately, and the lithium level was measured by atomic absorption spectrophotometry. The pharmacokinetic parameters were as follows: K12 (microconstant) = 0.3455 +/- 0.5345 (mean +/- SD) h-1; K21 (microconstant) = 0.1691 +/- 0.1242 h-1; K10 (microconstant) = 0.1320 +/- 0.1112 h-1; Vl (volume of distribution of central compartment) = 16.9057 +/- 5.9384 1; Vss (volume of distribution at steady state) = 38.8917 +/- 11.4540 1; V-beta (volume of distribution of elimination phase) = 46.3809 +/- 13.8742 1; alpha (distribution rate constant) = 0.5932 +/- 0.7090; and beta (excretion rate constant) = 0.0361 +/- 0.0141. The mean elimination half-life, AUC (the area under the curve) and clearance were 22.5 +/- 9.9 h (range from 9.6 to 50.4 h), 16.33 +/- 5.52 mmoll-1h (8.69 to 31.81 mmoll-1 h), and 1.65 +/- 0.53 1h-1 (0.76 to 2.28 1h-1) or 28.59 +/- 9.58 ml/kg-1 h-1, respectively. There were no statistically significant differences in beta, AUC and clearance between Taiwanese/Chinese and Danish results. The possibility of lowering the traditional prophylactic therapeutic range of lithium to around 0.5-0.8 mmol/L is supported by the results of this study.

The lithium index, a ratio of erythrocyte (intracellular) to plasma (extracellular) lithium concentrations, were studied by in vitro method in 22 healthy volunteers, 15 men and 17 women. Their mean age was 31.0 +/- 4.6 years (ranging from 26 to 41 years). In the study design, 20 ml of venous blood was taken from each subject into a test tube containing sodium citrate at the room temperature and erythrocytes were separated from plasma immediately. Then, the whole procedures for preparation and determination of lithium index were performed by using Pandey's method. Lithium levels were measured by atomic absorption spectrophotometry. Values of lithium index in vitro thus obtained were: 0.43 +/- 0.13 (range, 0.23-0.73) in men plus women; 0.37 +/- 0.10 (range, 0.23-0.57) in men; 0.49 +/- 0.13 (range, 0.26-0.73) in women. Women had a significantly higher Li+ index in vitro than men (t = 2.86, d.f. = 30, p less than 0.005). The possible reasons for the difference of the Li+ index in vitro between our result and other studies were discussed.