Resistance and Sensitivity to Digitalis

The average doses of digitalis required for the initial digitalization and subsequent maintenance of the heart patient are well known, but the averages do not indicate the range of individual differences encountered from one patient to another. Resistance to digitalis, and to the glycosides derived from it, is illustrated by the histories of four patients. It is sometimes impossible to give enough digitalis to slow down a tachycardia without inducing nausea, vomiting, pulsus bigeminus, or other signs of intoxication. Extreme sensitivity to digitalis is illustrated by the histories of three patients who exhibited intoxication with amounts of digitalis generally regarded as safe and usually given with impunity. Such sensitiveness has been seen after digitalis leaf, digoxin, digitoxin, and acetylstrophanthin. Awareness of the range of digitalis tolerance is essential if digitalis is to be used safely and effectively. Single-dose methods are hazardous. Digitalis should be given in divided doses, and the process of digitalization should be thought of as an individual biological titration.