Calcium Channel Blockers (CCB) Flashcards
What is the importance of calcium ions?
Calcium ions play a key role in the electrical excitation of cardiac cells and vascular smooth muscle cells
What do calcium channel blockers interfere with?
CCB drugs interfere with inward movement of calcium ions across myocardial and vascular smooth muscle cells
What are the activities possessed by calcium channel blockers?
Possess vasodilating activity
Where do calcium channel blockers drugs bind?
CCB drugs bind to receptors on voltage-gated calcium ion channels (L, N, & T) – results in maintenance of these channels in an inactive/closed state
What is the end result of calcium channel blockers binding?
calcium influx is decreased and reduced intracellular calcium
What calcium channel blockers are selective for AV node?
Phenylalkylamines & benzothiazepines
What calcium channel blockers are selective for arteriole beds?
Dihydropyridines
What are common side effects of calcium channel blockers?
systemic hypotension, peripheral edema, flushing, headache
What are the MOA of calcium channel blockers?
All clinically used CCB drugs bind to a unique site on the α-1 subunit of the L-type calcium channel (slow channel) which reduces entry of calcium ions into cells
What is Ca++ influx through L-type calcium channels responsible for?
phase 2 of the cardiac action potential and excitation-contraction coupling in cardiac/vascular smooth muscle & depolarization in SA & AV nodal tissue
What does blockade result in?
- Blockade results in slowing of heart rate
- reduced contractility
- decreased activity at SA node
- decreased speed of conduction through AV node
- vascular smooth muscle relaxation (decrease in BP)
- treat coronary vasospasm
- increase coronary blood flow
- treat angina
Review action poteintal in pacemaker cells- automaticity.
Review smooth muscle contraction.
Review smooth muscle contraction diagram.
What are the three classifications of calicum channel blockers?
Phenylalkylamine, Dihydropyridines and Benzothiazepine
What calicum channel blockers are Phenylalkylamine?
Verapamil
What calicum channel blockers are Dihydropyridines?
Nifedipine, Nicardipine, Nimodipine, Isradipine, Felodipine, Amlodipine
What calicum channel blockers are Benzothiazepine?
Dilitazem
What is the MOA of Verapamil?
Binds to α1 subunit of L-type Ca++ channel when open
What is the effects of Verapamil?
- Depresses AV node
- neg chronotropic effect SA node
- neg inotropic effect exaggerated in patients w/LV dysfunction
- moderate dilation coronary arteries
What cardiac conditions should Verapamil be avoided in?
- heart failure with bradycardia
- SA node dysfunction
- AV block
- effect enhanced with β blockade
What is the relationship between Verapamil and Wolff-parkinson white syndrome?
Avoid: Wolff-Parkinson White (WPW) syndrome - can result in antegrade conduction resulting in wide-complex VT deteriorating into VF
What the uses of Verapamil?
- SVT (AV node action)
- essential HTN
- vasospastic angina
What has replaced adenosine for Verapamil?
Replaced by adenosine for SVT
When are the pharmacological effects of Verapamil seen?
2-3 min after IV
What is the elimination half time of Verapamil?
6-12 hours (prolonged in liver disease)
What is the IV dose of Verapamil?
IV dose 2.5-10 mg (infusion 5 mg/h) per Nagelhout
What is the metabolism of Verapamil? What is produced?
Hepatic metabolism with active metabolite norverapamil that is renally excreted
What is the protein binding of Verapamil?
Highly protein bound (90%) and may be affected by other drugs such as lidocaine, diazepam, propranolol
What do Dihydropyridines prevent?
Prevent Ca++ entry with an extracellular modulation of L-type Ca++ channel with primary effect on peripheral arterioles and cerebral vessels
What Dihydropyridines have effects on your peripheral arterioles?
nifedipine, nicardipine, clevidipine, isradipine, amlodipine, felodipine
What Dihydropyridines have effects on your cerebral vessels?
nimodipine
What can acute administration of dihydropyridines can result in?
reflex tachycardia d/t reduced BP leading to SNS activity or baroreceptor reflex
What is the clinical uses of Dihydropyridines?
treatment of HTN
What is the the clinical use of nimodipine sl?
tx of post SAH vasospasm
What are other uses of Dihydropyridines?
- Raynaud syndrome
- cluster HAs
- angina
- certain dysrhythmias
What are the properties of Nifedipine?
Greater coronary and peripheral artery vasodilating properties than verapamil
What effects the offset of Nifedipine clinical properties?
Negative inotropic, chronotropic, chromotropic effects offset by sympathetic reflex