Diabetes insipidus, nephrogenic lithium treatment

The answer is c. (Katzung, p 493.) Lithium treatment frequently causes polyuria and polydipsia. The collecting tubule of the kidney loses the capacity to conserve water via anti diuretic hormone. This results in significant free-water clearance, which is referred to as nephrogenic diabetes insipidus. 

The long-term toxic effects of lithium, such as nephrogenic diabetes insipidus, which has been calculated to occur in up to 5% of patients, and the rare possibility of lithium combined with neuroleptics being neurotoxic, has stimulated the research for other drug treatments. However, apart from the neuroleptics, these drugs have not been studied as extensively in the treatment of acute mania, but are worthy of consideration because of their reduced side effects. 

Polydipsia and polyuria are common but reversible concomitants of lithium treatment, occurring at therapeutic serum concentrations. The principal physiologic lesion involved is loss of responsiveness to antidiuretic hormone (nephrogenic diabetes insipidus). Lithium-induced diabetes insipidus is resistant to vasopressin but responds to amiloride. 

In a cross-sectional study of 12 octogenarians (average age 84 years) who had taken lithium for an average of 54 months (mean serum concentration 0.42 mmol/1), none became toxic and none had to stop treatment because of adverse effects. Transient renal function abnormalities were noted one patient developed nephrogenic diabetes insipidus and one became hypothyroidic (510). For lithium therapy in very old people, the authors advised close monitoring in a specialized setting. 

Rabin EZ, Garston RG, Weir RV, Posen GA. Persistent nephrogenic diabetes insipidus associated with long term lithium carbonate treatment. Can Med Assoc J 1979 121 (2) 194-198. 

Confusion, mood changes, decreased sexual interest, and weight gain are symptoms that may be unrelated to drug administration. On the other hand, psychiatric drugs, including those used in the treatment of psychotic and affective disorders, may be responsible for such symptoms. Tremor and symptoms of nephrogenic diabetes insipidus are characteristic adverse effects of lithium that may occur at therapeutic blood levels of the dmg. The answer is (D). 

In dehydrated patients, replace fluid deficits with intravenous crystalloid solutions. Initial treatment should Include repletion of sodium and water with 1-2 L of normal saline (children 10-20 mL/kg). Once fluid deficits are replaced, give hypotonic (eg, half-normal saline) solutions because continued administration of normal saline often leads to hypernatremia, especially in patients with lithium-induced nephrogenic diabetes insipidus. 

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