<p>Intravenous Adenosine injection has been effectively administered in the presence of other cardioactive drugs, such as Quinidine, beta- adrenergic blocking agents, Calcium channel blocking agents and angiotensin converting enzyme inhibitors without any change in the adverse reaction profile. Digoxin and Verapamil use may be rarely associated with ventricular fibrillation when combined with Adenosine. Because of the potential for additive or synergistic depressant effects on the SA and AV nodes, however, Adenosine should be used with caution in the presence of these agents. The use of Adenosine in patients receiving Digitalis may be rarely associated with ventricular fibrillation. The effects of Adenosine are antagonized by Methylxanthines, such as, Caffeine and Theophylline.</p>