Calcium antagonists/ channel blockers

Question 1

What are some examples of calcium antagonists + some channel blockers

Answer 1

• Diltiazem, verapamil

- Amlodipine, nifedipine

Question 2

When are the indications for use

Answer 2

• 1st/2nd line Tx hypertension (reduce risk stroke, MI, CVD death)
• Control symptoms in STABLE ANGINA (B-blockers = main alt)
• Control cardiac rate in supraventricular arrhythmias (diltiazem) e.g. SVT, AF, A flutter

Question 3

What are some side effects

Answer 3

Amlodipine/ nifedipine =
- Ankle swelling, flushing, headache, palpitations
(vasodilation + compensatory tachy)

Verapamil =
constipation, + rarely bradycardia, heart block, HF

Diltazem = mixed vascular + cardiac action = many effects

Question 4

What are some contraindications

Answer 4

Verapamil/ diltiazem

• Poor ventricular function (worsen HF)
• AV nodal conduction delay (may cause complete heart block)

Amlodipine/ nifedipine

• Unstable angina (vasodilation = reflex increase contractility + tachy = ^ O2 demand)
• Sev aortic stenosis

Question 5

What are some interactions

Answer 5

Diltiazem/verapamil (non-dihydropyridine Ca channel blockers)
- X B-blockers - may cause HF, bradycardia, asystole

Question 6

What is the mechanism of action

Answer 6

• Decrease Ca2+ entry into vascular & cardiac cells
• reduces intracellular Ca conc = relaxation & vasoD in arterial sm. Muscle = lowering arterial pressure
• Reduces myocardial contractility & suppress cardiac conduction across AV node = slowing ventricular rate.
• Reduced O2 demand preventing angina.