05-12-2008, 07:18 PM
hen used concomitantly, non-dihydropyridine-type calcium channel blockers (e.g. verapamil, diltiazern) and 13adrenergic blocking agents can have additive negative effects on heart rate, AV node conduction, and myocardial contractility. Significant sinus bradycardia (or even occasionally sinus arrest with an AV junctional or idioventricular rhythm) and hypotension may occur. Patients taking combinations of these medications should be carefully monitored.
(Choice A) Nifedipine is a dihydropyridine calcium channel blocker with minimal effects on the sinoatrial node and cardiac conduction. It acts predominantly as a vasodilator and can cause a reflex increase in heart rate. It would be unlikely to cause synergistic slowing of the SA node firing rate when combined with a 6-blocker.
(Choice B, D and E) ACE inhibitors (e.g. captopril), nitrates and peripheral a1-selective adrenergic blockers (prazosin) predominantly cause vasodilatation and reflex tachycardia. Bradycardia is not expected.
(Choice A) Nifedipine is a dihydropyridine calcium channel blocker with minimal effects on the sinoatrial node and cardiac conduction. It acts predominantly as a vasodilator and can cause a reflex increase in heart rate. It would be unlikely to cause synergistic slowing of the SA node firing rate when combined with a 6-blocker.
(Choice B, D and E) ACE inhibitors (e.g. captopril), nitrates and peripheral a1-selective adrenergic blockers (prazosin) predominantly cause vasodilatation and reflex tachycardia. Bradycardia is not expected.