Effect of New Target Therapeutic Serum Digoxin Concentration Range on the Incidence of Digoxin Toxicity and the Clinical Efficacy.

Our previous study suggested that maintaining the serum digoxin concentration (SDC) in a lower target range (0.5-1.4 ng/ml) than the generally recommended range (0.5-2.0 ng/ml) may be useful to avoid the occurrence of digoxin toxicity in elderly patients (over 71 years old). Thus, the present prospective clinical study was carried out to evaluate the significance of the new target therapeutic SDC range in decreasing the incidence of digoxin toxicity during digoxin maintenance therapy in elderly patients.Study subjects who received oral maintenance therapy with digoxin for heart failure and/or atrial fibrillation with tachycardia included 899 patients and 946 patients in 1995 and 1997, respectively at Kosei Hospital. In all study subjects, measurements of SDC, blood chemistry analysis, and 24-hour Holter electrocardiographic recording were performed when the SDC was at a presumed steady state.After treatment of patients with a lower SDC range, the incidence (1.8%) of digoxin toxicity in 1997 was significantly less than that (7.3%) in 1995. In addition, the incidence (2.6%) of adverse reactions of patients over 71 years old in 1997 was also markedly lower than that (16.4%) in 1995. In 83 elderly patients, no significant difference in heart rate under conditions of resting and exercise was observed between patients with SDCs over 1.4 ng/ml (mean SDC 1.79 ng/ml) and patients with SDCs less than 1 .4 ng/ml (mean SDC 1.26 ng/ml).These results indicate that the treatment of elderly patients with the new therapeutic SDC range reduces the incidence of digoxin toxicity with an equivalent therapeutic efficacy to that obtained with the generally recommended range.