Possible Interaction: Adenosine and Verapamil

“Both verapamil and propranolol can exhibit additive effects with adenosine in prolonging AV nodal conduction time; however, only verapamil can reduce the dose of adenosine required to produce AV nodal block.”

“However, verapamil , in contrast to propranolol, significantly reduced the dose of adenosine required to produce AV nodal block, from 4.4 +/- 0.7 mg to 2.7 +/- 0.3 mg (p < 0.01).”

“In conclusion, the negative dromotropic effects of adenosine are preserved and independent even in the presence of verapamil , propranolol, or procainamide.”

“This finding indicates that the dose of adenosine may be reduced for patients who have already been treated with verapamil.”

“However, given the high incidence of minor but unpleasant side effects in patients treated with adenosine and the potential for hypotension with verapamil , patients should be fully informed of these risks prior to treatment.”

“ Verapamil had an additive effect to adenosine on slowing retrograde VA conduction, which further supports the evidence that the retrograde fast pathway in part involves an AV nodal-like structure.”

“The overall efficacy of adenosine (89%) was significantly greater than that of verapamil (61%; p < 0.05).”

“ Adenosine , in concentrations achieved in the plasma during myocardial ischemia (0.01-0.1 microM), enhanced the inhibitory effects of nifedipine, verapamil and diltiazem on platelet aggregation 5-100 fold.”

“In conclusion, adenosine and verapamil given at dosages with comparable effect on the AV node have markedly different effects on different pacemakers in the same heart.”

“ Adenosine added exogenously inhibited electrically evoked-contraction of the atrium, but not that of the papillary, although inhibitions by verapamil of the contractions were approximately equal in these preparations.”

“However, when hearts were treated with both verapamil and adenosine (10(-4) M), recovery of both ATP and PCr content was significantly greater than that of control hearts.”

“ Verapamil , 5-25 microM, potentiated the increased glucose output and vasoconstriction observed in response to adenosine.”

“Hence, the adenosine-verapamil interaction has clinical implications for conditions in which release of adenosine is increased (e.g. myocardial ischemia) or adenosine is administered in the presence of verapamil.”

“In Group I, control dogs, adenosine increased SCL by 82 +/- 21 msec before vs. 185 +/- 35 msec 15 minutes after verapamil , respectively (p less than 0.05).”

“In this group adenosine prolonged sinus cycle length maximally by 270 +/- 41 msec before verapamil , but following verapamil this effect of adenosine was transiently attenuated with a maximal sinus cycle length prolongation of only 165 +/- 24 msec (10 minutes following verapamil) (p less than 0.05, vs. before verapamil).”

“These data indicate that the autonomic nervous system modulate the interactive negative chronotropic effects of adenosine and verapamil in the canine sinus node.”