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Calcium channel blockers

How they work

Calcium channel blockers are cardiac drugs with a wide range of effects. Ultimately, they block the Ca2+ channels in the heart and blood vessels. Since there are many types of these channels, there are many different effects that various CCBs have.

Some, like verapamil, function quite like beta blockers, making the heart pump slower and less hard. Others, like nifidipine mostly dilate blood vessels in the heart and body, meaning they are used to treat angina. There is also a class, approximately halfway between the two, where the heart is affected a little, and the blood vessels a little -diltiazem is one of these.

What are they used for

  • Reducing blood pressure in hypertension[1]. They are part of the first line treatment for old or afrocarribean hypertensives[2].
  • Relieving angina
  • Verapamil used to be used for arrhythmias, but these days there are much better drugs.

Common types and dose

  • Amlodipine - angina or hypertension 5-10mg OD.
  • Nifidipine - prophylaxis of angina, or for Raynaud's 5mg-20mg TDS.
  • Diltiazem - angina or hypertension 60mg TDS, upto 120mg.

Side effects

Many of the CCBs have multiple preparations; short term and long term. The short term ones are not recommended for managing hypertension, as they can cause reflex tachycardia.

Many of them, probably as a result of the vasodilation, cause ankle swelling which diuretics don't really help with. Diltiazem shows this side effect less than amlodipine.

As with anything that drops blood pressure, they can cause hypotension. They can also cause headache, and like beta blockers, should not be used in patients with heart block.

References

  1. "Effects of ACE Inhibitors, Calcium Antagonists, and Other Blood Pressure lowering Drugs " by RB Thakkar and S Oparil - Current Hypertension Reports. Volume 3, Number 3, 227-228, DOI: 10.1007/s11906-001-0043-5
  2. "Hypertension: management of hypertension in adults in primary care" - NICE 2006. http://www.nice.org.uk/nicemedia/live/10986/30114/30114.pdf