Calcium Channel Blockers Flashcards
Where do Ca channel blockers have the greatest impact?
Heart and blood vessels
Ca channel blockers effects
Vasodilation- smooth muscle relaxation, lower BP
Therapeutic doses- dilate peripheral and heart arterioles, with no significant effect on veins
Effects of CCBs on the heart
Decrease in force of contraction
Slowing of electrical impulses through the heart
Dihydropyridines (nifedipine) site of action
arterioles
Verapamil and diltiazem site of action
act on the arterioles AND the heart.
Verapamil and Diltiazem
acts on vascular smooth muscle and the heart
Lowers BP and HR
Verapamil and Diltiazem Hemodynamic effects
Reduce arterial pressure
Increase coronary perfusion
Reduce HR- blockade at SA and AV node
Relax the heart, decrease force of heart contraction.
No net effect on cardiac performance
Uses for verapamil
Angina pectoris
HTN
atrial flutter, afib, paroxysmal supraventricular tachycardia
Migraines
Verapamil adverse effects
Constipation- especially severe for the elderly, add fiber Dizziness Flushing/redness Headache Heart block
(diltiazem the same except for less constipation)
Drug interactions of verapamil
Digoxin
Beta-adrenergic agonists
Toxicity of verapamil
Severe hypotension Bradycardia and AV block Ventricular tachydysrhythmias Treated with atropine, epinephrine, gastric lavage Especially possible if given IV
Nifedipine
Blocks calcium channels ONLY IN THE BLOOD VESSELS
vasodilates by blocking Ca flow into the vacular smooth muscle
Cannot be used for dysrhythmias. Safer for those with AV blocks.
Lowers BP
Adverse effects of nifedipine
Flushing
Dizziness
Headache
Reflex tachycardia
How to prevent reflex tachycardia with nifedipine?
Combine with a beta blocker
Rapid acting nifedipine
Increased mortality in patients with MI and unstable angina— prefer slow release
