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Calcium-channel blockers: Nursing Pharmacology

Notes

Notes

CALCIUM-CHANNEL BLOCKERS
DRUG NAME
Dihydropyridines: nifedipine (Procardia, Adalat), amlodipine (Norvasc), clevidipine (Cleviprex), nicardipine (Cardene), felodipine (Plendil), nimodipine (Nimotop)

Non-dihydropyridines: diltiazem (Cardizem), verapamil (Calan, Isoptin)
CLASS
Calcium Channel Blockers (CCB)
MECHANISM OF ACTION
  • Block the entry of calcium into the cells
  • Reduce the contraction of vascular smooth muscle and cardiac muscle
    • Dilate arterioles, and reduce blood pressure and peripheral vascular resistance
    • Dilate coronary vessels and increase oxygen supply to the heart
    • Reduce force of contraction of cardiac muscles and reduce oxygen demand of the heart
  • Reduce the firing and conduction of impulse through the SA and AV nodes in the heart
INDICATIONS
  • Cardiac arrhythmia, hypertension, angina pectoris, tocolysis in preterm labor, Raynaud’s phenomenon, migraine prophylaxis
  • Nimodipine: subarachnoid hemorrhage
ROUTE(S) OF ADMINISTRATION
  • PO
  • IV
SIDE EFFECTS
  • General: headache, dizziness, flushing of the skin, peripheral edema, hypotension
  • Dihydropyridines: reflex tachycardia, gingival hyperplasia
  • Non-dihydropyridines: bradycardia, constipation and hyperprolactinemia
CONTRAINDICATIONS AND CAUTIONS
  • Pre-existing bradycardia
  • Heart block
  • Heart failure
  • Use with caution: hepatic and renal disease
  • Interactions: digoxin, grapefruit
NURSING CONSIDERATIONS: CALCIUM-CHANNEL BLOCKERS
ASSESSMENT AND MONITORING
  • Vital signs, CBC, sodium, potassium, creatinine, BUN, liver function tests, and urinalysis, ECG
  • For angina: frequency and severity of symptoms
  • Monitor for side effects and therapeutic response
CLIENT EDUCATION
  • Purpose of medication
  • Self-administration
    • Take exactly as prescribed, do not stop abruptly
    • Swallow whole; do not divide, crush, or chew
    • Avoid grapefruit juice and limit caffeine
  • Side effects
    • Hypotension and reflex tachycardia: change positions slowly
    • Peripheral edema: elevate legs
    • Constipation: increase fiber and fluids
    • Gingival hyperplasia: good dental hygiene
  • Lifestyle modifications for cardiovascular health
  • Heart rate and blood pressure self-monitoring
  • Report persistent side effects, hypotension, bradycardia; seek medical attention if angina not relieved by rest or medication
Memory Anchors and Partner Content
Transcript

Calcium channel blockers are medications that are primarily used to treat cardiac arrhythmias, hypertension, and angina pectoris.

Calcium channel blockers are used to a lesser extent for prophylaxis of migraines and for symptomatic treatment of Raynaud phenomenon, which is caused by reduced blood flow in tiny peripheral vessels.

Finally, calcium channel blockers also relax uterine smooth muscle, which is useful to prevent premature uterine contractions, and this can help delay preterm labor.

Now, calcium channel blockers can be administered orally or intravenously, and are divided into two main groups, dihydropyridines and non-dihydropyridines.

Dihydropyridines include amlodipine, nicardipine, nifedipine, felodipine, and clevidipine, which have a more potent action on the blood vessels, specifically the arterioles, than the heart.

As a result, they’re preferred to treat hypertension. Another dihydropyridine is nimodipine, which has the added benefit of being able to cross over the blood-brain barrier.

So, it can be used to prevent or treat cerebral vasospasm caused by an aneurysmal subarachnoid hemorrhage.

On the other hand, non-dihydropyridines include verapamil and diltiazem, which have a more potent action on the heart than the blood vessels.

Verapamil is highly selective for cardiac calcium channels; and, thus, is mainly used to treat angina pectoris and arrhythmias.

Diltiazem is equally good at blocking both cardiac and vascular calcium channels, and so it’s effective in hypertension and arrhythmias.

Now, once administered, calcium channel blockers block voltage-gated calcium channels, and they act by decreasing the amount of calcium entering the cell.

Normally, calcium is required for the contraction of both the cardiac muscles and the vascular smooth muscles. So, the decreased calcium reduces the muscle’s ability to contract, ultimately relaxing them.

Now, calcium channel blockers relax vascular, particularly arterial, smooth muscles, which helps reduce the blood pressure, and peripheral vascular resistance, or the afterload, which is the pressure that the heart must work against to eject the blood.

At the same time, in the heart, calcium channel blockers relax the coronary vessels, which improves the oxygen delivery to the heart; and they also reduce the force of contraction of the cardiac muscles, which reduces the oxygen demand of the heart.

Additionally, calcium channel blockers prevent the depolarization of cardiac pacemaker cells in the SA and AV nodes, which are responsible for generating and maintaining the heart rate

This way, these medications reduce the firing and conduction of the impulses through these nodes, eventually decreasing the heart rate.

Now, the vasodilatory action of calcium channel blockers may also lead to some side effects, including headache, dizziness, flushing of the skin, peripheral edema, and hypotension, which is more common with dihydropyridines.

Moreover, hypotension can trigger reflex tachycardia, in order to maintain adequate tissue perfusion. Finally, dihydropyridines can also cause gingival hyperplasia, the cause of which is still unclear.

On the other hand, non-dihydropyridines decrease the heart rate and contractility, so they can cause additional side effects like bradycardia, constipation, and hyperprolactinemia.

Now, due to their depressive action on the heart, non-dihydropyridines, and to a lesser extent, dihydropyridines, are contraindicated in clients with pre-existing bradycardia, heart block, and heart failure.

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