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

In spite of the continued uncertainty about the clinical significance of differences in the Lithium Ratio, the authors and others have been studying factors which determine the distribution of Li⁺ across the RBC membrane in an effort to understand the considerable intersubject variation which has been observed by all investigators. In brief, it appears that the major reason for interindividual variation in the magnitude of the Lithium Ratio is the Li-Na counterflow system.