[Predictive capacity of 3 methods for estimating the maintenance dose of digoxin in elderly patients]

To evaluate three methods for digoxin dose adjustment in aged patients.

We determined the plasma digoxin levels that would be attained in 47 consecutive old patients with doses adjusted to the creatinin clearance (Clc) by means of three mathematical functions.

Age: 79.1 +/- 6.1 years of age; Clc: 0.77 +/- 0.24 mL/kg of lean body weight and minute. Once the dose has been fitted to the digoxin pharmacokinetic parameters described in the bibliography, the drug levels would oscillate between 0.8 and 2.0 ng/mL in 85.1% of the patients, with a 95% confidence interval (95% CI) from 72.3% to 92.6%; in 0.0% of the patients the levels would be greater than 2 ng/mL (95% IC: 0.0% to 7.6%). The precision and the bias would be 0.40 ng/mL (95% IC: 0.33 to 0.46 ng/mL) and--0.08 ng/m (95% IC: -0.19 to 0.04 ng/mL), respectively. The drug level would not be associated with the Clc (coefficient of Clc in the regression line: -0.0003; P > 0.9). The results would be worse with the others two mathematical functions.

The first of the above adjustment methods would lead to good results if digoxin has not been prescriped in order to control the cardiac frequency in the setting of auricular fibrillation.