The Applicability of International Reports on Digoxin Toxicity to Iranian Patients

Background: The striking similarities between signs and symptoms of digoxin intoxication and clinical picture of primary congestive heart failure (CHF) make their diagnosis relatively difficult. Narrow therapeutic window of digoxin and increasing mortality and morbidity due to its intoxication make serum digoxin measurements an essential point of concern. Objectives: The aims of present investigation were to study digoxin therapeutic and toxic levels in Iranian patients and to evaluate the applicability of most clinical findings in relation to digoxin toxic levels. Patients and Methods: Serum digoxin levels of 195 patients with heart failure, who used digoxin for at least 10 days, were evaluated by radioimmunoassay. Patients’ clinical and electrocardiographic (ECG) manifestations of digoxin toxicity were evaluated and compared with serum digoxin level. Therapeutic range of digoxin in patients to be used as a reference was 0.9 to 2.3 ng/ml. Results: Twenty-one patients showed both clinical and ECG signs of digoxin toxicity, 19 patients had only a single manifestation and 155 did not present with any of these manifestations. Although the serum digoxin level in patients was of great importance, our results showed that clinical manifestation was not completely related to serum digoxin level. Conclusion: Considering the narrow therapeutic window of digoxin, periodical monitoring of serum digoxin levels must be conducted in all patients receiving digoxin. Nevertheless, clinical manifestation of digoxin toxicity was not sufficient to be used for evaluation of drug toxicity.