Plasma and erythrocyte kinetic considerations in lithium therapy.

Developments in the analysis and pharmacokinetics of lithium, and the role of the pharmacist in the management of lithium therapy in affective disorders, are described. Research showing that lithium levels in the brain may be better predicted from erythrocyte lithium levels than plasma levels is reviewed. Also reviewed is lithium kinetics in affective disorders. The pharmacist (1) determines relevant aspects of the patient's condition, (2) develops an appropriate blood sampling schedule, (3) initiates and maintains a serial lithium erythrocyte and plasma patient profile, (4) evaluates erythrocyte and serum levels in relation to established criteria to provide a basis for differential diagnosis of the patient, and (5) individualizes lithium dosage and schedules. Four cases are used to illustrate this approach. It is suggested that outpatient mental health clinics would be likely settings for the further development of this clinical role.