Self-poisoning and therapeutic intoxication with lithium.

Of 68 admissions for lithium overdose over 16 years, 25 were due to therapeutic intoxication and 43 to deliberate self-poisoning. Three patients with therapeutic intoxication had acute diabetes insipidus with hypernatraemia. One of them had acute renal failure requiring dialysis, prolonged Parkinsonism and generalised myopathy. Twenty-two patients with therapeutic intoxication had peak serum lithium concentrations above the therapeutic range. In contrast, of 22 self-poisoned patients with peak serum lithium concentrations above the therapeutic range only 3 developed toxicity. The mean admission plasma urea concentration in patients with therapeutic intoxication was higher than in self-poisoned patients and the mean admission plasma bicarbonate concentration was lower. The mean serum lithium half-life in 8 patients with therapeutic intoxication was considerably longer than in 5 self-poisoned patients. Renal lithium clearance is enhanced by increased sodium excretion and we recommend that lithium toxicity be treated with saline diuresis and frusemide if fluid retention occurs. Haemodialysis is mandatory when renal failure is present, and may be indicated when serum lithium concentrations are very high or rising rapidly.