[Digoxin level as a limited drug toxicity indicator in the assessment of post-digitalis arrhythmia].
A clinical-laboratory analysis was carried out in 18 patients on long-term treatment with digoxin in whom toxic arrhythmia occurred, taking into account serum digoxin level measurement. In 11 patients the toxic arrhythmia correlated with high digoxin concentration in blood, in six cases it was observed with the concentration of the drug within the therapeutic level range, and in one patient it was seen below this range. Blood digoxin level in patients with hypokalemia was significantly lower in comparison to those with normal serum potassium level. Severe clinical condition of patients, especially elderly persons with hypokalemia, respiratory acidosis and renal failure contributes to the development of toxic arrhythmia; for this reason it is useful to apply in these patients the therapy monitored by blood level of the drug. Electrocardiographic features of digitalis action and non-cardiac adverse effects were seldom observed in patients with toxic arrhythmia.