High blood pressure and calcium channel blockers

Lesley Dobson / 20 July 2017

What are calcium channel blockers and how do they help lower blood pressure? Find out with our guide.



Calcium Channel Blockers are often prescribed for people who have high blood pressure. They work by preventing calcium from making our blood vessels become narrow, and increasing our blood pressure. CCBs, as they are commonly known, usually only cause mild side effects, if any.

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How do calcium channel-blockers (CCBs) work?

Calcium channel blockers (CCBs) are a type of drug that is used to treat high blood pressure. They are also used to treat some other conditions, including angina, coronary heart disease and irregular heart rhythms (also known as arrhythmias).

There are two different types of CCBs. The Dihydropyridines, for instance, Nifedipine, help to reduce your blood pressure by relaxing your blood vessels and arteries.

The second type of CCBs, non-dihydropyridines, do the same job, but also have another function. They help to reduce some abnormal heart rhythms that can make you feel dizzy, and can cause atrial fibrillation.

Calcium-channel blockers prescribed for patients in the UK

There are a number of CCBs that can be prescribed in the UK. Your doctor will choose the medication they feel is most suitable for your condition

Medicine name Amlodipine Brand names Amlostine, Exforge, Istin

Medicine name Diltiazem Brand names Adizen-SR, Adizem-XL, Diltiazem, Dilzem SR, Dilzem XL, Slozem, Tildiem, Tildiem LA, Tildien Retard, Viazem XL

Medicine name Felodopine Brand names Felotens XL, Plendil, Triapin, Triapin Mite, Vascalpha

Medicine name Isradipine Brand name Prescal

Medicine name Lacidipine Brand name Motens

Medicine name Lercanidipine Brand name Zanidip

Medicine name Nicardipine Brand name Cardene

Medicine name Nifedipine Brand names Nifedipine Adalat, Adalat LA, Adalat Retard, Beta-Adalat, Coracte XL, Nifedipress, Tenif, Tensipine

Information taken from Blood Pressure UK’s website.

CCBs work by cutting down the amount of calcium that enters the cells of our heart and the walls of our blood vessels. We need calcium, and not just to keep our bones strong.  Calcium is also important because it plays a part in the process of contracting our blood vessels. These include the arteries that carry vital oxygen-carrying blood to our hearts.

However, calcium can also narrow our blood vessels. When this happens it makes our blood pressure rise. By preventing our blood vessels from narrowing CCBs allow blood to carry on flowing steadily through them, and so help reduce our blood pressure. (Calcium-channel blockers are also sometimes known as calcium antagonists).

Who would be given calcium-channel blockers (CCBs)?

Calcium channel blockers are one of the more popular drugs for treating high blood pressure, and are often a doctor’s first choice for treating patients who have high blood pressure. If you are over 55, or have African Caribbean origins, these may be the first blood pressure drugs your doctor prescribes for you.

This is especially likely to be the case if you have quite high blood pressure. However, as you grow older, your chances of developing side effects from this type of drug increase. Older people can take CCBs, but will often be given a lower dose than younger people. Or your doctor or medical team may decide to try another drug or combination of drugs, to see if this keeps your blood pressure under control without causing unpleasant side effects.

Depending on how well you respond to the CCB medication your doctor prescribes; you may just need to take that drug. However, if yours isn’t working well enough to deal properly with your health problems, your doctor may also prescribe other medications to take as well. As with all drug treatments, it may take a little while to work out the best combination of drugs for you.

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Who would not be given calcium-channel blockers (CCBs)?

For most people CCBs are usually safe, and are unlikely to react with any other drugs you’ve been prescribed. However, there are some instances when your doctor will need to keep a close eye on you.

If you have health problems with your kidneys or liver, your doctor may still prescribe a CCB. However, they will monitor you carefully to make sure that this medication doesn’t interfere with other drugs you are taking for existing health problems. The same applies if you have abnormal heart rhythms and heart failure.

Calcium channel blockers can cause some side effects (although these are relatively rare). You may, however, on starting a course of CCBs, have swollen ankles, some dizziness, headache, and flushing (see Side effects of CCBs, below).

Side effects of calcium channel blockers

In most cases CCBs don’t cause serious, or any, side effects. If you’re going to have side effects these tend to appear when you first take a new medicine. Those side effects that do happen, tend to be fairly minor, and don’t cause very much discomfort.

CCBs work by making your blood vessels relax, so they become wider. Because of this some people can become flushed (look red in the face and chest), and develop headaches.

With some CCBs you may also develop constipation. You can deal with this in the usual way – by drinking plenty of water, and increasing your intake of fruit and vegetables. If things don’t improve it may be worth talking to your GP about changing your medication.

Other side effects can include pain in your ankles or feet, swollen ankles, feeling tired and/or dizzy, flushing, and heart palpitations (rapid heart beats).

Generally these side effects only last for a few days. If they continue for a longer period, talk to your GP, to see if they can suggest an alternative blood pressure medication. However, it is unusual for CCBs to have serious side effects

Another important point to remember is that you shouldn’t drink grapefruit juice when taking CCBs. This is because grapefruit juice has the effect of letting more of your medication into your blood stream. This can make your blood pressure drop rapidly, and without warning which could cause a dangerous situation. If this happens you could need urgent medical help.

Drug and food interactions you should know about

NICE guidelines for taking CCBs

Patients under 55

Step 1

People under 55 can be given an ACE inhibitor to start off with. Unless there is an urgent need to lower a patient’s blood pressure very quickly for medical reasons, (for instance, if your blood pressure is so high that it is dangerous for your health) it’s normal for patients to stay on the same medication for about four weeks. This allows the medical team to check how patients are responding to the treatment.

If the ACE inhibitor treatment isn’t working as it should, your doctor will probably suggest a different type of medication to lower your blood pressure. This is likely to be an angiotensin-II receptor antagonist. If this doesn’t work, or makes you ill, other choices are beta-blockers. (However, these aren’t generally recommended for patients with diabetes, or those at risk of diabetes.

Step 2

At this stage, an ACE inhibitor or an angiotensin-II receptor antagonist in combination with a calcium-channel blocker will probably be your doctor’s first choice for many people under 55 with high blood pressure.

However, if you can’t tolerate a calcium-channel blocker, or if your doctor finds evidence that you have heart failure, or that you are at high risk of heart failure, they may prescribe a thiazide-related diuretic (one example is indapamide).

Step 3

Your doctor is likely to consider prescribing you an ACE inhibitor or angiotensin-II receptor antagonist, along with a calcium-channel blocker and a thiazide-related diuretic

Step 4

At this stage you are likely to be classed as having resistant hypertension, which means that your high blood pressure has become more resistant to treatment. Because of this your doctor may consider taking advice from a specialist to help treat your situation.

Your doctor may also try different medications, such as a low dose of spironolactone or they may use a high dose of a thiazide-related diuretic, if your condition calls for this.

Your doctor will also monitor your renal function – how well your kidneys are working – and your electrolytes. (These are substances that are vital for our good health. They ensure that our cells and organs continue working well. Electrolytes include bicarbonate, chloride, potassium and sodium.) They may also consider treating you with an alpha-blocker or a beta-blocker.

Patients aged over 55, and patients who have African or Caribbean origins

Step 1

People over 55, and those who have African or Caribbean origins are usually prescribed a calcium channel blocker – CCB. If this isn’t suitable, or the patient has a high risk of heart failure, your doctor may prescribe a thiazide-related diuretic, such as chlortalidone or indapamide instead.

Step 2

Treatment advice at this stage includes a Calcium Channel Blocker (CCB) or a thiazide-related diuretic.  These should be taken alongside an ACE inhibitor, or an angiotensin II receptor antagonist.

An angiotensin II receptor antagonist, along with a calcium-channel blocker tends to be a more suitable treatment for patients who have African or Caribbean origins.

Step 3

Your doctor is likely to consider prescribing an ACE inhibitor or angiotensin-II receptor antagonist for you, along with a calcium-channel blocker and a thiazide-related diuretic

Step 4

At this stage you are likely to be classed as having resistant hypertension, which means that your high blood pressure has become more resistant to treatment. Because of this your doctor may consider taking advice from a specialist to help treat your situation.

Your doctor may also try different medications, such as a low dose of spironolactone, or may use a high dose of a thiazide-related diuretic, if your condition calls for this.

Your doctor will also monitor your renal function – how well your kidneys are working – and your electrolytes. They may also consider treating you with an alpha-blocker or a beta-blocker.

(NICE is the National Institute for Health Care and Excellence

Steer clear of grapefruit juice when you are taking Calcium Channel Blockers.

Interactions with calcium channel blockers

Steer clear of grapefruit juice when you are taking CCBs. It can trigger or increase the risk of side effects with some calcium channel blockers. According to the British Heart Foundation these can include nifedipine, diltiazem and verapamil.

You should also avoid taking St John’s wort, the herbal extract. This can affect your medication so that it doesn’t work as effectively. Make sure you always read the instructions that come with your drugs, and let your GP or pharmacist know if you start having unusual reactions to any medication.

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