[Digoxin poisoning in patients of 2 geriatric departments in London: prevalence and mortality].

Digoxin is a toxic drug with a narrow therapeutic index that is mostly used by the elderly. Although it is accepted that toxicity of digoxin occurs more frequently in elderly than in younger patients, there is dispute about its prevalence and associated mortality. A study was therefore set up to, on the one hand, find the prevalence and associated mortality of digoxin toxicity in patients admitted onto two geriatric wards in London and, on the other hand, to study the relationship between serum digoxin level and age, serum urea, serum potassium and serum calcium in geriatric patients with digoxin toxicity. Over a period of three years 1438 patients (age 75-93) were admitted of whom 452 (31%) were on digoxin. Thirty-five patients (7.7%) were diagnosed as having digoxin toxicity. Eight patients (22.9%) with digoxin toxicity died during admission. Mortality was higher although not statistically significant for the patients with toxicity than for the patients who were on digoxin without toxicity. The fatal outcome was not predicted by age, serum urea, serum potassium or serum calcium. The serum digoxin level of the eight patients who died was lower than the level of those (n = 23) who survived. Four patients (11%) had a normal serum digoxin level and clinical features of digoxin toxicity that disappeared on stopping digoxin. A hypothesis is put foreward to explain the weak association between serum digoxin level and digoxin toxicity in geriatric patients.