CALCIUM CHANNEL BLOCKERS

Therapeutic uses

The 3 classes of CCB differ in their chemical structure AND more importantly, in their selectivity for cardiac vs. vascular calcium channels. Therefore...

...the therapeutic effects of different CCBs vary A LOT!

Dihydropyridines

Examples of specific drugs

Examples: Amlodipine, Felodipine, Nifedipine, Nimodipine, Nicardipine (note: all of them end in '-pine'!)

Dihydropyridines (DHPs) cause peripheral and coronary vasodilation.

Use in:

HTN
Acute life-threatening HTN (IV nicardipine)
Angina
Aneurysmal SAH (nimodipine)
Raynaud's phenomenon (nifedipine)

Hypertension

CCBs are the 1st-line anti-hypertensive for older patients and of Afro-Caribbean family origin (see NICE flowchart).

NICE recommends use of any ACE inhibitor for the treatment of hypertension.

DHPs are often given in slow-release formulations to make them more tolerable. Typically the patient is started on a low dose and titrated up until blood pressure is in target range (see BNF for guidance on each drug).

IV nicardipine can be used in the treatment of acute life-threatening HTN.

Hypertension

Stable angina

Dihydropyridine CCBs are given for angina when:

there are contraindications or adverse reactions to β-blockers
β-blocker monotherapy has been unsuccessful so a CCB is added

Dihydropyridine CCBs reduce the frequency of angina and improve exercise tolerance (see IMAGE study).

How do dihydropyridine CCBs work in angina?

By reducing arterial blood pressure they reduce cardiac afterload and therefore the work of the left ventricles. This reduces the myocardial oxygen demand and the incidence of myocardial ischaemia.

Cerebral artery vasospasm

Nimodipine has a high affinity for cerebral vessels and so preferentially causes cerebral vasodilatation and relieves vasospasm of the cerebral arteries.

It is given in the emergency setting to prevent or treat ischaemia following aneurysmal subarachnoid haemorrhage.

Nicardipine has similar effects and can be used to prevent cerebral vasospasm associated with stroke.

Raynaud's phenomenon

Nifedipine is used for symptomatic relief in patients who experience Raynaud's phenomenon - a phenomenon where vasospasm of small arterioles supplying peripheries causes paraesthesia in response to cold temperatures or stress.

Whilst nifedipine shows no physiological benefits, it has been shown to significant reduce number of attacks and provides symptomatic benefit (see Aldori et al, 1986).

Verapamil

Verapamil has cardiac depressing effects, which include reducing heart rate (negative chronotropy), reducing heart contractility (negative inotropy) and reducing the speed of conduction in the heart (negative dromotropy). It also causes peripheral vasodilatation.

Use in:

Angina
HTN
Supraventricular arrhythmias
Cluster headache prophylaxis (specialist prescription)

Avoid in:

Heart failure
Conduction disorders (e.g. heart block)
Bradycardia
patients also on B-blockers

Hypertension

CCBs are the 1st-line anti-hypertensive for older patients and of Afro-Caribbean family origin (see NICE flowchart).

Verapamil should not be given to patients with heart failure as its cardiac depressing effects may induce decompensation.

Stable angina

Verapamil may be given for angina when:

there are contraindications or adverse reactions to β-blockers.

Verapamil should NOT be given with a β-blocker due to combined cardiac depressing effects may cause heart block or decompensated heart failure.

How does verapamil work in angina?

Verapamil reduces the frequency of angina and improves exercise tolerance (see Brodsky et al., 1982)

Verapamil's cardiac depressing effects and blood pressure lowering effects which reduce the oxygen requirements of the myocardium and reduce the incidence of myocardial ischaemia.

Supraventricular arrhythmias

Verapamil can be given orally or IV for the management of supraventricular tachyarrhythmias including:

Paroxysmal SVT
Atrial flutter
Atrial fibrillation (with fast ventricular response rate)

Conduction system

Cluster headache

Verapamil is given under specialist supervision for the prophylaxis of episodic cluster headache.

Diltiazem

Diltiazem has both vasodilating and cardiac depressing effects (but to a lesser extent than verapamil).

Use in:

Angina
HTN

Avoid in:

HF
Conduction disorders (e.g. heart block)
Bradycardia
patients also on B-blockers

Hypertension

CCBs are the 1st-line anti-hypertensive for older patients and of Afro-Caribbean family origin (see NICE flowchart).

Diltiazem should not be given to patients with heart failure as its cardiac depressing effects may induce decompensation.

Stable angina

Diltiazem may be given for angina when:

there are contraindications or adverse reactions to β-blockers
the cardiac depressing effects of verapamil are considered too potent

Diltiazem reduces the frequency of angina and improves exercise tolerance (see Hossack et al., 1982).

How does diltiazem work in angina?

By reducing arterial blood pressure it reduces cardiac afterload and therefore the work of the left ventricles. This combined with diltiazem's cardiac depressing effects reduces the myocardial oxygen demand and the incidence of myocardial ischaemia.

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