Calcium channel blockers

Question 1

Name 4 calcium channel blockers.

Answer 1

Verapamil
Diltiazem
Amlodopine
Felodopine

Question 2

How do Calcium channel blockers principally lower BP?

Answer 2

By arterial vasodilation.

Question 3

Give the 3 common clinical indictions for use of Calcium channel blockers.

Answer 3

1) Amlodipine can be used as a first or second line treatment for HTN to reduce risk fo stroke, MI or CVD.
2) All Calcium channel blockers can be used for symptom control in patients with stable angina. Beta blockers are the main alternative to this.
3) Diltiazem and Verapamil are used to control cardiac rate in patients with supraventricular arrhythmias (AVT, atrial flutter, AF).

Question 4

State the mechanism of action of calcium channel blockers.

Answer 4

Decrease Ca entry into vascular and cardiac cells > reduces intracellular Ca conc > relaxation and vasodilation in arterial smooth muscle > lowers arterial pressure.

Question 5

1) What is the action of Calcium channel blockers in the heart?
2) What does reduced cardiac rate, contractility and afterload do?

Answer 5

1) Reduce myocardial contractility and suppress cardiac conduction (particularly across AVN, slowing the ventricular rate)
2) Reduces myocardial oxygen demand, preventing angina.

Question 6

1) What are dihydropyridines and give examples.

2) What are non-dihydropyridines and give some examples.

Answer 6

1) Calcium channel blockers more selective for vasculature
(Amlodipine).

2) Calcium channel blockers more selective for the heart (Verapamil)

Question 7

List some adverse effects of Calcium channel blockers, along with the specific drugs that can cause them.

Answer 7

• Amlodipine: ankle oedema, flushing, headache, palpitations caused by vasodilation and compensatory tachycardia.
• Verapamil: commonly causes constipation, and less commonly bradycardia, heart block and cardiac failure.
• Diltiazem has effects on both vasculature and the heart so can cause any of the above.

Question 8

Which patients should Verapamil and Diltiazem be used with caution in?

Answer 8

Patients with poor LV funciton as they can precipitate or worsen heart failure/ avoided in patients with AVN conduction delay as this could promote complete heart block.

Question 9

Give 2 contraindications to the use of Amlodipine.

Answer 9

Avoid in patients with unstable angina - vasodilation causes reflex increase in contractiltiy and heart rate, increasing myocardial oxygen demand.
Avoid in patients with severe aortic stenosis as use of this can cause collapse.

Question 10

What drugs should not be used in combination with Calcium channel blockers and why?

Answer 10

Calcium channel blockers and beta blockers should not be used in combination as they are both negatively chronotropic and inotropic, and so together can cause heart failure, bradycardia and asystole.