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CALCIUM CHANNEL BLOCKERS

What are the types of Calcium Channel Blocker?

They are a group of similar drugs, with names often ending in "...pine": nifedipine (Adalat), diltiazem (Tildiem, Adizem), felodipine (Plendil), isradipine (Prescal), lacidipine (Motens), amlodipine (Istin), nicardipine (Cardene), verapamil (Cordilox, Securon, Univer), nimodipine (Nimotop), nisoldipine (Syscor) and lercandipine (Zanidip).

What are Calcium Channel Blockers for ?

Calcium channel blockers are mainly used to treat high blood pressure or angina (chest pain due to poor blood circulation to the heart muscle). These drugs will reduce the risk of stroke and heart attack and are therefore very important. Verapamil and nimodipine are different to the other calcium channel blockers. Verapamil can be used to treat some types of uneven heartbeat as well as high blood pressure and angina. Nimodipine is not used for heart or blood pressure problems. It is given to people who have had bleeding from blood-vessels in the brain. It prevents spasm of the blood-vessels, which could in turn cause further brain damage.

How do Calcium Channel Blockers work ?

Calcium must enter cells in the walls of blood-vessels before they can narrow down or constrict. By not letting the calcium enter these cells, calcium channel blockers make blood-vessels widen. Since blood can then flow through more easily, blood pressure will fall. For the same reason, the heart has less work to do, and this reduces any strain on the heart. Angina will then improve. By widening the coronary arteries which carry blood to the heart muscle, more blood is also supplied to the heart itself. Verapamil works directly on the heart. It slows the heartbeat and reduces the strength of each beat. This reduces the strain on the heart in angina and less blood is pumped, so the blood pressure falls. Verapamil also interrupts the nerve impulses which pass through the heart to trigger each heartbeat. This is why it is useful for correcting some types of uneven heartbeat.

How should Calcium Channel Blockers be used ?

You should take your calcium channel blocker regularly every day, whether you feel well or not. Some are taken several times a day. Others may be in slow-release tablet or capsule form and can be taken less often. Check the label!

During Treatment

If you are taking a calcium channel blocker for high blood pressure, you may not feel any benefit. Only measuring the blood pressure regularly will tell you that it is controlled. You are taking the calcium channel blocker to prevent damage to your health in the long term. If you are taking the drug for angina, chest pains should become less frequent. When you do get pain, it should not be as bad as before. You may find you can do things which were previously not possible. Most side-effects of calcium channel blockers are worst when you first start taking them, and will disappear as you carry on with the treatment. You may get headache, flushing and dizziness. The dizziness is caused by a fall in your blood pressure, and you should tell your doctor if this happens to you. It may be necessary to lower the dose of your calcium channel blocker. Because the drop in blood pressure is worst when you first start treatment, you should take the first few doses sitting down. This should ensure that you do not faint if your blood pressure falls. These drugs can also cause a rash, lethargy or tiredness. You should tell your doctor if this happens to you. In a few people, calcium channel blockers can make angina worse instead of better. If you start to get chest pains more often than you did before you started treatment, do tell your doctor straight away. You will need to have a different drug to treat your angina.

Drug Interference

Another type of blood pressure tablet called an ACE inhibitor (usually ending with "...pril") makes calcium channel blockers cause an even bigger fall of blood pressure. This can be useful for treatment. However, it may cause dizziness or fainting if your blood pressure falls too low. If you take another type of blood pressure tablet called a beta-blocker, the heartbeat can slow down too much, your blood pressure may fall too much, and heart failure might actually develop. Here again, when used in the correct doses, these drugs often work very well together. Calcium channel blockers and drugs for epilepsy interfere with each other. Calcium channel blockers increase both the good effects and possibly the side-effects of drugs for epilepsy. The dose may need to be changed. In turn, drugs for epilepsy reduce the effect of some calcium channel blockers. Calcium channel blockers either reduce the effect or increase the side-effects of several drugs for heartbeat irregularities. The blood levels of an important heart drug called digoxin in blood are increased by several of the calcium channel blockers, increasing the risk of harmful effects from digoxin. Diltiazem and verapamil increase both the wanted and the unwanted effects of theophylline, a drug used in the treatment of asthma.

What if Calcium Channel Blockers are not taken ?

If you forget to take a dose at your usual time, you should take it as soon as you remember. If your next dose is due in less than 2 hours, take a dose now, and miss the next dose. You should not stop taking your calcium channel blocker unless your doctor tells you to. You may start to have chest pains more often. Your blood pressure may rise again, putting you at risk from a stroke or heart attack.

General advice on the use of Calcium Channel Blockers

If you are pregnant, think you could be pregnant, or want to become pregnant while you are taking a calcium channel blocker, you should tell your doctor. Some calcium channel blockers have caused problems in the offspring of pregnant animals. It is therefore wise to avoid them unless there is no suitable alternative. If you have any questions not covered in this leaflet, please ask your pharmacist or doctor: Keep this leaflet handy.