RESUMO
The pharmacokinetics of digoxin have been studied in eight healthy volunteers, 23 congestive cardiac failure and 10 chronic renal failure patients. The mean serum digoxin concentrations in the volunteers and the congestive cardiac failure patients were significantly different (P less than 0.001) from those in the chronic renal failure patients. The mean half-life of digoxin in the healthy volunteers (37.2 h +/- 8.6 s.d.) was comparable to the widely accepted 40 h for digoxin half-life in normal individuals. Half-life was significantly prolonged in renal failure patients. There was a good inverse correlation, in the three groups, between serum creatinine and creatinine clearance, but the expected close correlation between the renal clearance of digoxin and serum creatinine was not demonstrated, probably because this was an oral study. There was no statistically significant difference in the age and weight in all three groups. There was also no significant difference in all parameters, measured and derived, between the volunteers and the congestive cardiac failure patients. However, when the volunteers and/or the congestive cardiac failure patients were compared with the renal failure patients, there was a significant difference in all parameters except age and weight. Thus, in the absence of renal impairment and hypokalaemia, standard dosages of digoxin can be used in congestive cardiac failure patients, provided symptoms and signs of toxicity are constantly monitored. Therapeutic drug monitoring of digoxin is desirable in view of its low toxicity: therapeutic ratio, and its kinetics should be studied in detail in each community to establish correct dosages to prevent and manage digoxin toxicity.