Possible Interaction: Quinidine and Digitalis

“A therapeutic combination of digitalis and quinidine may produce resolution of the arrhythmia in the presence of altered ventricular function or when AF is of an uncertain onset.”

“This therapy may restore sinus rhythm, but conversion to sinus rhythm often requires the combined use of digitalis with a β-blocker or class I antiarrhythmic drug ( quinidine , disopyramide, procainamide, propafenone, or flecainide).”

“In the last decade of the 20th century, much of the toxicity of digitalis therapy was attributed to its combined use with quinidine.”

“Whereas quinidine and digitalis have been used concomitantly for years, dramatic elevations in blood digoxin levels have been observed.”

“In a 90‐year‐old man undergoing prolonged digitalis therapy, digitalis toxicity was precipitated by the administration of quinidine.”

“6 It is recommended that close monitoring of digoxin concentration and appropriate reduction of the maintenance dose is undertaken when quinidine is to be given to patients on digitalis therapy.”

“Therefore, the lengthening of these intervals in subjects taking digitalis after the addition of quinidine represents more than just the negative inotropic effect of quinidine, and occurs despite the increase in serum digoxin concentration.”

“Although the possible danger of simultaneous administration of large doses of digitalis and quinidine ”

“In some patients receiving both digitalis and quinidine , the atrial rate showed less of a tendency to slow or actually increased, resulting in atrial fibrillation followed by normal sinus rhythm.”

“On rare occasions both digitalis and the subsequent administration of quinidine are ineffective.”