Tolterodine-induced hyponatraemia

Management of electrolyte abnormalities is challenging in older people as the sensation of thirst, renal function and hormonal modulators of the milieu interior are often impaired. Furthermore, the complex effects of ageing upon these homeostatic mechanisms are often superimposed upon a background of chronic disease, malnutrition and co-existent medications. Hyponatraemia is one of the commonest electrolyte abnormalities, occurring in approximately 7% of healthy elderly persons. Hyponatraemia may only come to light when some other ailment prompts investigations or hospital admission. Drug-induced hyponatraemia is common in older people and is most commonly associated with diuretics and SSRI/SNRI antidepressants, but has also been reported with a wide range of other drugs. We believe this is the first case report of hyponatraemia due to tolterodine.