CH 48 Calcium Channel Blockers

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Calcium Channel Blockers

Drugs that prevent calcium from entering cells, impacting heart and blood vessels.

Overall effects of Calcium Channel Blockers

Prevent calcium from entering cells, greatest impact on heart and blood vessels.

Therapeutic Uses of Calcium Channel Blockers

hypertension, angina pectoris, and cardiac dysrhythmias.

Physiologic Functions of Calcium Channel Blockers

Calcium channels open lead to contraction, while closed channels lead to vasoconstriction.

Pathophysiology of Therapeutic Doses of Calcium Channel Blockers

• Selectively act on peripheral arterioles and arteries 

• Selectively act on peripheral arterioles of the heart

• No significant effect on veins 

Direct effects of Verapamil and Diltiazem

Blockade at arterioles and the heart.

Five direct hemodynamic effects of verapamil and diltiazem

1. Blockade at peripheral arterioles 

(reduces arterial pressure)

2. Blockade at arteries and arterioles of heart 

(increases coronary perfusion)

3. Blockade at SA node

(reduces heart rate)

4. Blockade at AV node **MOST IMPORTANT

(Decreases AV nodal Conduction )

5. Blockade in the Myocardium 

(decreases force of contraction)

Indirect hemodynamic effects of Verapamil and Diltiazem

Activates baroreceptor reflex: decreases blood pressure.

Therapeutic uses of verapamil

• Angina pectoris (vasospastic angina and angina of effort)

• Essential hypertension (second-line agent after thiazide diuretics)

• Cardiac dysrhythmias (atrial flutter, atrial fibrillation, paroxysmal supraventricular tachycardia)

migrane

supraventricular tachycardia:

heart rate of 150+; heart rate so fast that chambers cannot fill adequately

Adverse effects of Verapamil

Common effects include constipation, dizziness, facial flushing, headache, edema, gingival hyperplasia, and heart block.

why is constipation a common side effect of Calcium Channel Blockers?

inhibits calcium influx in intestinal smooth muscle, leading to decreased motility and delayed gastrointestinal transit.

Drug interactions of Verapamil

Interactions with digoxin and beta-adrenergic blocking agents.

Toxicity of Verapamil

Results in severe hypotension, bradycardia, AV block, and ventricular tachydysrhythmias.

How to treat verapamil Toxicity

• perform Gastric lavage (wash out stomach with saline) and activated charcoal

Nifedipine

A dihydropyridine calcium channel blocker that acts mainly on vascular smooth muscle.

Overall effects of Nifedipine

Significant blockade of calcium channels in blood vessels leading to vasodilation.

Indirect effects of Nifedipine

• Lowered Blood pressure and activates baroreceptor reflex (Primarily with immediate vs sustained release)

• Increased heart rate

• Increased contractile force

Therapeutic uses of Nifedipine

Used for angina pectoris and hypertension, also investigational for migraine relief and preterm labor.

Adverse effects of Nifedipine

Include flushing, dizziness, headache, peripheral edema, gingival hyperplasia (gum swelling), chronic rash, reflex tachycardia, and increased cardiac oxygen demand.

Beta Blockers effect on adverse effects of Calcium Channel Blockers 

Beta blockers decrease adverse effects with Nifedipine (dihydropyridine) and intensify adverse effects with verapamil and diltiazem (nondihydropyridine)