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.
In addition, calcium channel blockers should be used cautiously in clients with hepatic
or renal disease, as well as when combined with digoxin, which is an antiarrhythmic medication,
as clients can develop digoxin toxicity by reducing its action and elimination.
Finally, clients on calcium channel blockers must avoid consuming grapefruit, as their
interaction can result in toxicity.
Nursing Considerations & Client Education Now, if your client is prescribed a calcium
channel blocker, be sure to obtain their baseline heart rate and blood pressure and review the
results of their lab results, including CBC, sodium, potassium, creatinine, BUN, liver
function tests, and urinalysis, as well as their electrocardiogram, or ECG.
If your client is taking a calcium channel blocker for angina pectoris, remember to ask
them about the frequency and severity of their angial symptoms.
Be sure your client understands how the medication helps control their symptoms, and instruct
them to take their medication exactly as instructed and to not stop taking it abruptly.
Let them know that they can take their medication with or without food, and that extended release
tablets should not be divided, crushed, or chewed.
Stress the importance of avoiding grapefruit and grapefruit juice, which can increase the
blood level of their medication; and advise them to limit caffeine consumption as well,
since it can increase blood pressure and heart rate.
Then, teach your client how to take their pulse and blood pressure, and to contact their
healthcare provider if they experience hypotension or bradycardia.
If their medication is prescribed for angina, stress the importance of seeking medical assistance
immediately if they experience angina that is not relieved by rest or medication.
Finally, reinforce cardiovascular health promotion by teaching your client about lifestyle modifications,
such as maintaining a healthy weight, smoking cessation, reducing their intake of sodium
and alcohol, and increasing physical activity.
Next, talk to your client about how to manage the common side effects of calcium channel
blockers.
Let them know that they may experience dizziness, hypotension, and reflex tachycardia, and that
they should change positions slowly to prevent falls.
If your client develops peripheral edema in the ankles and feet, encourage them to elevate
their legs for a few hours each day.
Remind your client how increasing their daily intake of fluid and fiber can help reduce
the risk of constipation.
Also stress the importance of good dental hygiene to prevent gingival hyperplasia.
Lastly, prompt your client to contact their healthcare provider if any of these adverse
effects are persistent or become bothersome.
During treatment, monitor your client’s blood pressure, heart rate, and anginal symptoms
for therapeutic effects of the medication.
Finally, continue to monitor for side effects and report any changes in the client’s condition
to the healthcare provider.
Alright, as a quick recap…
Calcium channel blockers are medications that are used to treat cardiac arrhythmias, hypertension,
angina pectoris, and other conditions.
These medications work by blocking calcium channels in the vascular smooth muscles and
cardiac muscles, which in turn helps them to relax.
Non-dihydropyridines have a more potent action on the heart than dihydropyridines, so they
are used more often to treat arrhythmias and angina pectoris, while dihydropyridines exert
their effects primarily in the blood vessels, so they are more often used to treat hypertension.
Nursing considerations for calcium channel blockers center around completing a thorough
baseline assessment; providing client education for safe self-administration and dealing with
side effects such as hypotension, bradycardia a