Clinical and Interpretive

Measurement of lithium is useful in monitoring therapy of patients with bipolar disorders, including recurrent episodes of mania and depression and evaluating lithium toxicity.

Lithium alters the intraneuronal metabolism of catecholamines by an unknown mechanism. It is used to suppress the manic phase of manic-depressive psychosis.

Lithium is distributed throughout the total water spaces of the body and is excreted primarily by the kidney. Toxicity from lithium salts leads to ataxia, slurred speech, and confusion. Since the concentration of lithium in the serum varies with the time after the dose, blood for lithium determination should be drawn at a standard time, preferably 8 to 12 hours after the last dose (trough values). There is no relationship between peak concentration and degree of intoxication.