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CH 48 Calcium Channel Blockers


  • Calcium Channel Blockers aka Calcium antagonists, slow channel blockers 

Overall effects and MOA

  • Drugs that prevent calcium from entering cells 

  • Greatest impact on heart and blood vessels  

Therapeutic Uses of calcium channel blockers 

  • Hypertension

  • Angina pectoris

  • Cardiac dysrhythmias 

* controversy of safety for patients with hypertension and diabetes 

Physiologic Functions and Consequences of a Blockade 

Vascular Smooth Muscle 

  • Calcium channels open= contractile process

  • Calcium channels closed = vasoconstriction

Therapeutic doses

  • Selectively act on peripheral arterioles and arteries 

  • Selectively act on peripheral arterioles of the heart

  • No significant effect on veins 


  • Verapamil and Diltiazem (Nondihydropyridines)

^Act on arterioles and the heart 

Overall effects and MOA

  • Direct effects on the heart and blood vessels 

  • Indirect reflex effects (heart rate increases and blood pressure decreases)

Five direct hemodynamic effects of verapamil and diltiazem  

  • Blockade at peripheral arterioles 

(reduces arterial pressure)

  • Blockade at arteries and arterioles of heart 

(increases coronary perfusion)

  • Blockade at SA node

(reduces heart rate)

  • Blockade at AV node **MOST IMPORTANT

(Decreases AV nodal Conduction )

  • Blockade in the Myocardium 

(decreases force of contraction)

Indirect hemodynamic effects of verapamil and diltiazem

  • Baroreceptor reflex (pressure sensor to maintain Blood Pressure)

Net effects of verapamil and diltiazem

  • little/no effect on cardiac performance 

  • Vasodilation accompanied by reduced arterial pressure and increased coronary perfusion 

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

** supraventricular tachycardia: heart rate of 150+; heart rate so fast that chambers cannot fill adequately

  • Migraine 

Adverse effects of verapamil

^Beta Blockers INTENSIFY adverse effects

  • Constipation **most common

  • Results blockade of calcium channels in smooth muscle of intestines (decreased peristalsis)

  • Especially severe for older adults 

  • Can be decreased by increasing fiber and fluids 

  • Dizziness 

  • Facial flushing: : due to relaxed arteries 

  • Headache 

  • Edema of ankles and feet: due to relaxed arteries 

  • Gingival hyperplasia: gum swelling 

  • Heart block: electrical pathway is impaired; communication not working 

Drug interactions of verapamil

  • Digoxin: slows down heart rate

  • Beta-adrenergic blocking agents 

Verapamil Toxicity 

  • Severe hypotension 

  • Bradycardia and AV block 

  • Ventricular tachydysrhythmias

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

Note: IV verapamil for dysrhythmias can be used for severe cardiovascular effects (Monitor Blood pressure and ECG; resuscitation equipment should be immediately available) 


  • Nifedipine [adalat, Nifedical, Nifediac, Procardia] (Dihydropyridines)

^Act mainly on vascular smooth muscle

Overall effects and MOA

  • Significant blockade of calcium channels in blood vessels 

  • Minimal blockade of calcium channels in heart

  • Results in vasodilation 

  • Cannot be used to treat dysrhythmias 

  • Less likely than verapamil to exacerbate preexisting cardiac disorders 

Direct effects of Nifedipine

  • Blockade of calcium channels in vascular smooth muscle 

  • Vasodilation by blocking calcium channels

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

  • Angina pectoris 

  • Hypertension 

  • Relieve migraine and suppress preterm labor (investigational basis)

Adverse effects of Nifedipine

^Beta Blockers decrease adverse effects

  • Flushing 

  • Dizziness 

  • Headache 

  • Peripheral edema 

  • Gingival hyperplasia 

  • Chronic eczematous rash in older patients 

  • Increases cardiac oxygen demand

  • Reflex tachycardia (can be combined with beta blocker to prevent reflex tachycardia)

**Note: Immediate release/rapid acting Calcium Channel blockers have been associated with increased mortality in patients with MI and unstable angina