Unstable angina / non ST elevation myocardial infarction calcium channel blockers


 * Associate Editors-In-Chief: ; Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.; Smita Kohli, M.D.;

Overview
Calcium channel blockers (CCBs) consist of three subclasses:
 * Dihydropyridines (e.g., nifedipine, amlodipine),
 * Phenylalkylamines (e.g., verapamil), and
 * Benzothiazepines (e.g., diltiazem).

Mechanism of Benefit
The degree of these effects varies amongst the three classes with nifedipine and amlodipine having the most peripheral arterial dilatory effects but few or no AV or sinus node effects, whereas verapamil and diltiazem having prominent AV and sinus node effects and but only some peripheral arterial dilatory effects.
 * CCBs inhibit both myocardial and vascular smooth muscle contraction.
 * They also cause AV block and sinus node slowing.

Although different CCBs are structurally and, potentially, therapeutically diverse, superiority of 1 agent over another in Unstable angina/NSTEMI has not been demonstrated, except for the increased risks posed by rapid-release, short-acting dihydropyridines such as nifedipine.

Indications

 * Calcium channel blockers may be used to control ongoing or recurring ischemia-related symptoms in patients who already are receiving adequate doses of nitroglycerine (NTG) and beta blockers, in patients who are unable to tolerate adequate doses of 1 or both of these agents, and in patients with variant angina.
 * Definitive evidence for a benefit of CCBs in Unstable angina/NSTEMI is predominantly limited to symptom control.
 * When beta blockers cannot be used, and in the absence of clinically significant LV dysfunction, heart rate–slowing CCBs are preferred.

==ACC / AHA Guidelines (DO NOT EDIT) ==

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Class I
1. In Unstable angina / NSTEMI patients with continuing or frequently recurring ischemia and in whom beta blockers are contraindicated, a non dihydropyridine calcium channel blocker (e.g., verapamil or diltiazem) should be given as initial therapy in the absence of clinically significant left ventricular dysfunction or other contraindications. (Level of Evidence: B)

Class IIa
1. Oral long acting non dihydropyridine calcium antagonists are reasonable for use in Unstable angina / NSTEMI patients for recurrent ischemia in the absence of contraindications after beta blockers and NTG have been fully used. (Level of Evidence: C)

Class IIb
1. The use of extended-release forms of non dihydropyridine calcium antagonists instead of a beta blocker may be considered in patients with Unstable angina / NSTEMI. (Level of Evidence: B)

2. Immediate-release dihydropyridine calcium antagonists in the presence of adequate beta blocker may be considered in patients with Unstable angina / NSTEMI with ongoing ischemic symptoms or hypertension. (Level of Evidence: B)

Class III
1. Immediate-release dihydropyridine calcium antagonists should not be administered to patients with Unstable angina / NSTEMI in the absence of a beta blocker. (Level of Evidence: A)}}