[On improved prophylaxis of endogenous-phasic psychoses: aspects of parallel determination of lithium in serum and erythrocytes (author's transl)].

In 30% of the psychiatric patients investigated the lithium concentration in erythrocytes (RBC-lithium) is a more reliable indicator for the evaluation of the clinical response and the risk of toxicity. After lithium administration the lithium RBC levels increased within the first three weeks. Lithium RBC/plasma ratios are not different between unipolar, bipolar and schizo-affective psychoses. It was found that low lithium RBC/plasma ratios correspond with low monoamine oxidase (MAO) activity in platelets.