Possible Interaction: Verapamil and Digitalis

“In the presence of chronic established atrial fibrillation, digitalis in combination with a β-blocking agent or a calcium antagonist, such as verapamil or diltiazem, may be useful to slow the ventricular response rate.”

“In atrial fibrillation with an ECG pattern of delta waves at the beginning of QRS complexes, digitalis and verapamil are contraindicated since they may induce ventricular fibrillation.”

“Within this group, the interaction of digitalis and verapamil is increasingly recognized as an important cause of digitalis toxicity.”

“We conclude that verapamil is effective in further suppressing the ventricular response rate in atrial fibrillation when given in combination with digitalis and can serve as an adjunct to digitalis therapy in the chronic management of patients with atrial fibrillation.”

“Therefore, verapamil appears to exert a protective effect against the development of digitalis-induced arrhythmia, possibly by suppressing delayed afterpotential generation, and significantly increases the dose of digitalis required to produce AV block.”