Erythrocyte concentrations of the lithium ion: Clinical correlates and mechanisms of action

When lithium carbonate is administered to individuals, there is considerable intersubject variation in the extent of accumulation of Li⁺ by erythrocytes. The primary reason for this is differences in the activity of a Li⁺-Na⁺ counterflow system, which, under clinical conditions, removes Li⁺ from the cell. It appears that some bipolar patients accumulate more Li⁺ in their red cells than either unipolar depressives or normal controls. The precise clinical characteristics of the bipolar patients who accumulate relatively large amounts of erythrocyte Li⁺ need to be clarified in future research. Finally, the measurement of red cell concentrations of Li⁺ in addition to the usual plasma measurement, can be used as an indicator of patient compliance.