Calcium channel blockers (CCBs) work by blocking voltage-gated calcium channels in the smooth muscle of the heart and blood vessels.
By reducing calcium influx, they cause vasodilation in the blood vessels and decrease the contractility and workload of the heart.
This results in lowered blood pressure and reduced oxygen demand by the heart, making them effective in treating cardiovascular diseases.

Indications

Hypertension: Calcium channel blockers are commonly used to lower blood pressure, especially in patients who cannot tolerate other antihypertensives.
Angina: They relieve angina by reducing heart workload and dilating coronary arteries to improve blood flow.
Arrhythmias: Non-dihydropyridine CCBs, such as verapamil and diltiazem, are effective in treating supraventricular tachycardias and controlling heart rate in atrial fibrillation.
Raynaud’s Phenomenon: Dihydropyridines like nifedipine are used to reduce vasospasm and improve blood flow in peripheral vascular conditions.

Drug Classification

Dihydropyridines: These mainly affect vascular smooth muscle, causing vasodilation. Common examples include amlodipine and nifedipine . They are primarily used for hypertension and angina.
Non-Dihydropyridines: These have a more pronounced effect on the heart and are used for arrhythmias. Examples include verapamil and diltiazem .

Delivery Forms

Oral: The most common route, available in both immediate-release and extended-release forms for daily management.
Intravenous: Used in acute settings, such as controlling arrhythmias or severe hypertension.

Side Effects

Peripheral Edema: Common with dihydropyridines due to vasodilation, particularly in the lower extremities.
Bradycardia: Especially seen with non-dihydropyridines, which affect heart rate.
Constipation: Particularly associated with verapamil due to its effect on smooth muscle relaxation.
Headache and Flushing: Caused by vasodilation and common with dihydropyridine CCBs.

Drug Interactions

Beta Blockers: Concomitant use with non-dihydropyridines can increase the risk of bradycardia and heart block.
Digoxin: Verapamil can increase digoxin levels, requiring careful monitoring to avoid toxicity.
Grapefruit Juice: May increase blood levels of certain calcium channel blockers, particularly dihydropyridines, leading to exaggerated effects.

Monitoring and Precautions

Monitor for heart rate and blood pressure , especially with non-dihydropyridine CCBs, as they can cause bradycardia and hypotension.
Check for symptoms of edema , especially in patients taking dihydropyridine CCBs.
Use caution in patients with heart failure , as CCBs can worsen symptoms in some cases, particularly non-dihydropyridines.

Common Calcium Channel Blockers: Names, Doses, and Indications

Generic Name (UK/US)	Brand Names (UK/US)	Typical Dose & Frequency	Indications
Amlodipine	Norvasc (US), Istin (UK)	5-10 mg once daily	Hypertension, angina
Nifedipine	Adalat (UK), Procardia (US)	30-90 mg once daily (extended-release)	Hypertension, angina, Raynaud's phenomenon
Verapamil	Isoptin (UK), Calan (US)	80-120 mg three times daily (IR); 180-240 mg once daily (ER)	Arrhythmias, angina, hypertension
Diltiazem	Tildiem (UK), Cardizem (US)	120-360 mg once daily (extended-release)	Angina, hypertension, arrhythmias
Felodipine	Plendil (US/UK)	5-10 mg once daily	Hypertension, angina
Nimodipine	Nimotop (UK/US)	60 mg every 4 hours	Subarachnoid haemorrhage (to prevent cerebral vasospasm)
Nicardipine	Cardene (US/UK)	20-40 mg three times daily (oral); IV for acute hypertension	Hypertension, angina, hypertensive emergencies (IV)
Clevidipine	Cleviprex (US)	1-21 mg/hour (IV infusion)	Hypertensive emergencies (IV only)

Patient Education

Explain potential side effects, such as swelling of the legs or flushing , so patients can recognize them early.
Encourage patients to avoid grapefruit juice if they are on dihydropyridines to prevent interactions.
Advise patients to report any new or worsening symptoms, including dizziness, bradycardia, or significant swelling.

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Calcium Channel Blockers

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