There is no increase in the overall mortality of patients undergoing long-term lithium treatment compared with those receiving short-term treatment. Lithium causes a reduction in the incidence of suicide in patients suffering from manic depressive illness. Long-term treatment with lithium is more effective than treatment with imipramine or amitriptyline. Drug interactions may cause problems during long-term therapy with lithium. A reduction in plasma levels of lithium should be considered in stable patients on long-term prophylaxis. Discontinuation of therapy often results in a relapse. The toxicity of lithium is related to its effects on calcium transport.