By lowering arterial pressure with subsequent reflex tachycardia, nifedipine may aggravate angina. This problem can be avoided with simultaneous use of beta blockers. Withdrawal of beta blockade in some patients taking nifedipine may worsen angina.
What are some of the important drug interactions of calcium channel antagonists?
Increased plasma digoxin levels Excessive hypotension
Hypotension, bradycardia, decreased quinidine level Increased carbamazepine levels Increased plasma level of calcium channel antagonist Increased cyclosporine levels Decreased effects of calcium channel antagonists
What are the signs and symptoms of calcium channel antagonist toxicity?
The most common toxic effects are hypotension and bradydysrhythmias. Of the latter, most common are AV block and sinus bradycardia with junctional escape rhythms. Rarely, one sees a slow idioventricular rhythm and prolonged QRS duration.