A patient arrives at the emergency department with symptomatic narrow complex tachycardia. The patient is hemodynamically stable. The decision is made to administer intravenous (IV) adenosine.
Under which of the following circumstances should the dosage of adenosine be reduced?
A. The patient is taking theophyllineThe patient is taking dipyridamole. Dipyridamole potentiates the effect of adenosine by interfering with metabolism; therefore, a reduced dose of adenosine is recommended. Although not a part of this question, it is important to remember that adenosine also needs to be used with extreme caution in heart transplant patients as a markedly exaggerated response to adenosine can be seen in the denervated heart. An increased dose of adenosine is recommended in the presence of methylxanthines such as theophylline, which antagonizes the effect of adenosine (blocks receptors), and other factors such as slow circulation time, valvular regurgitation, and left-to-right shunts that reduce the effectiveness of adenosine.