Digitalisation and digitalis detoxication in the elderly.

Twenty-three elderly patients with normal renal function were studied during digitalisation for cardiac failure or atrial fibrillation. Mean serum digoxin concentrations were in the therapeutic range from the fourth day in seven patients given digoxin 0.25 mg daily, from the second day in seven patients given 0.5 mg followed by 0.25 mg daily, and from the first day in nine patients given 0.75 mg followed by 0.25 mg daily. Toxic effects were not encountered in any patient. Serial measurement of serum digoxin concentrations in six patients recovering from digitalis intoxication, all of whom had severe renal impairment, allowed calculation of serum half-times (62 to 189 hours), and elimination constants (9 to 27% per day). The apparent volumes of distribution of digoxin were around 300 litres, and the apparent body contents of the drugs around 20-25 mug/kg body weight. Differences between these figures and those determined by others for younger patients seem mainly to reflect the consequences of renal impairment. If reasonable assumptions are made for fractional absorption, volume of distribution, and elimination constant, serum digoxin levels during digitalisation can be predicted, and are found to agree well with those observed.