Lithium-induced nephrogenic diabetes insipidus in older people

Presentation: we report two patients, The first is a 68-year-old woman who presented with a 2-day history of vomiting. She was hypernatraemic and her elevated serum sodium concentration did not improve initially, despite adeq uate fluid replacement. She subsequently developed polyuria and polydipsia. The second patient, a 77-year-old woman, presented with delirium and sever e hypernatraemia after being treated for a chest infection 1 week earlier. Both patients were on long-term lithium treatment. Investigation: in both the cases, a supervised water-deprivation test done after normalization of the blood biochemistry showed partial nephrogenic di abetes insipidus. Outcome: lithium was discontinued. Conclusion: older people on lithium-especially those requiring supportive c are-are at risk of severe hypernatraemia after an acute illness or if their fluid intake is restricted.