The distribution of lithium into cerebrospinal fluid, brain tissue and bile in man.

The concentration of lithium was determined in plasma, cerebrospinal fluid (CSF) and bile in two groups of 5 and 6 patients after oral administration of lithium carbonate (0.2 mVal/kg b.w.) in each group. In a third group of 7 patients the lithium concentration in the brain and also in the CSF and the plasma was determined in the steady state. The influx into CSF was delayed in contrast to that into plasma and bile. The elimination was biexponential. The mean plasma half-life of lithium carbonate was 21 hours. The concentration ratio between CSF and bile, respectively, and plasma was 0.44 +/- 0.03 and 1.48 +/- 0.36 in steady state. Two percent of the given dose was eliminated with the bile within 24 hours. There was no concentration difference in steady state between that for CSF and both white and grey brain matter. It is suggested that the concentration of lithium in CSF represents the brain concentration.