Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
25 Cards in this Set
- Front
- Back
|
How do calcium channel blockers function?
|
They prevent calcium ions from entering cells and initiating the contraction process of smooth muscle, causing vasodilation.
|
|
|
What conditions are treated using calcium channel blockers?
|
hyptertension, angina pectoris, and cardiac dysrhythmias.
|
|
|
Do calcium channel blocker affect arteries, veins, or both?
|
arteries and arterioles only
|
|
|
Which sites in the heart are regulated by calcium channels?
|
the myocardium, the SA node and the AV node
|
|
|
What effect does calcium have on the myocardium? What happens if the calcium channels are blocked?
|
force of contraction is increased. If the channels in atrial and ventricular muscle are blocked, contractile force diminishes.
|
|
|
What effect does calcium have on the SA node? What happens if the calcium channels are blocked?
|
Discharge of the node occurs with influx of calcium and the heart rate increases. If the calcium channels are blocked the heart rate decreases.
|
|
|
What effect does calcium have on the AV node? What happens if the calcium channels are blocked?
|
Calcium increases the velocity of conduction through the AV node, which coordinates contraction of venricles and atria. If calcium channels are blocked this conduction velocity is decreased.
|
|
|
What are the similarities between beta blockers and calcium channel blockers?
|
They both reduce force of contraction, slow heart rate and suppress conduction through the AV node.
|
|
|
What are the three families of calcium channel blockers? Where are their sites of action?
|
1. dihydropyridines (nifediprine) - arterioles
2. phenylalkylamine (verapamil) - arterioles and the heart 3. benzothiazepine (diltiazem) - arterioles and the heart |
|
|
Which drug was the first calcium channel blocker?
|
Verapamil
|
|
|
What are the five direct effects of Verapamil?
|
1. Reduction of arterial pressure by dilating peripheral arterioles
2. increased coronary perfusion by blocking arteries and arterioles of the heart 3. reduced heart rate by blocking calcium infusion of the SA node 4. decreases AV node conduction 5. decreased force of contraction by blocking calcium at the myocardium |
|
|
What is the overall cardiovascular effect of verapamil?
|
Vasodilation accompanied by reduced arterial pressure and increased coronary perfusion
|
|
|
How much of a dose of Verapamil actually reaches the systemic circulation?
|
20%
|
|
|
Where is Verapamil eliminated? As a result, are there any special considerations regarding dosage?
|
the liver
in patients with hepatic impairment, dosages must be substantially reduced to prevent toxicity |
|
|
What is the most common side effect of Verapamil?
|
constipation
|
|
|
What adverse cardiac side effects can occur with Verapamil?
|
1. Bradycardia due to blockade at the SA node
2. partial or complete AV block due to blockade at the AV node 3. decreased contractility due to blockade at the myocardium |
|
|
Which patients should not be given Verapamil?
|
Those with sick sinus syndrome, second-degree or third-degree AV block
|
|
|
What are the special considerations necessary when using Verapamil with Digoxin?
|
1. close monitoring due to increased suppression of AV node impulses
2. watch closely for signs of digoxin toxicity since Verapamil increases plasma levels of digoxin by about 60% |
|
|
Are there any special considerations when using Verapamil with beta blockers?
|
They should be administered several hours apart to avoid excessive cardiosuppression
|
|
|
What effect does grapefruit juice have on Verapamil levels?
|
They can raise them by 8 to 24 times by inhibiting thier ntestinal and hepatic metabolism
|
|
|
What are the signs of Verapamil toxicity?
|
severe hypotension, bradycardia, AV block, ventricular rachydysrhythmias
|
|
|
How do you treat Verapamil toxicity?
|
gastric lavage
|
|
|
What direct affects do dihydropyridines such as Nifedipine have on the cardiovascular system?
|
they block the calcium channels in vascular smooth muscle, causing vasodilation of the arterioles, lower arterial pressure and increased coronary perfusion.
|
|
|
Why can dihydropyridines such as Nifedipine cause reflex tachycardia? Which doses are most likely to do so?
|
The rapid reduction in blood pressure triggers the baroreceptor reflex. Only the fast acting formulation of these drugs results in a rapid drop in blood pressure.
|
|
|
What drugs can suppress the reflex tachycardia initiated by dihydropyridines?
|
beta blockers
|
