The active efflux of lithium from erythrocytes, expressed as the rate
constant ko, was studied in patients with primary affective disorder and in
controls. The authors' data suggest that ko is stable within individuals
over time, is inhibited during treatment with lithium carbonate, and may be
a good index of lithium toxicity. ko correlates significantly with the
lithium erythrocyte/plasma ratio but is seemingly not related to age, sex,
or affective disease subtype. Preliminary data suggest that ko may be
determined, at least in part, by a genetic factor.