Drug cabinet: Calcium channel blockers

Calcium Channel Blockers

Dr Kevin M O’Shaughnessy, Honorary Consultant and Senior Lecturer in Clinical Pharmacology at Addenbrooke’s Hospital, Cambridge, answers common questions about calcium channel blockers.

Calcium channel blockers (CCBs) are a group of medicines commonly prescribed to treat conditions of the heart and blood vessels, such as hypertension (high blood pressure), angina, some abnormal heart rhythms and Raynaud’s phenomenon (a condition resulting in painful and cold fingers and toes due to narrowing of the arteries in the hands and feet). You may be prescribed just a CCB or, if you have angina or high blood pressure, a combination of a CCB and another medicine if one medicine alone has not been effective in managing the issue.

How do CCBs work?

CCBs reduce the amount of calcium entering cells of the heart and blood vessel walls. This is significant because calcium is necessary to contract the muscular linings of blood vessels throughout your body (for example, the arteries that supply your heart with oxygen). Calcium passes into these cells through special pores in the surfaces of these cells called ion channels. These channels are blocked by CCBs, thereby reducing the amount of calcium entering cells of the heart and blood vessel walls. As a result, the blood vessels relax and the heart muscle receives more oxygenated blood, which is how CCBs are able to lower blood pressure and treat angina. Some CCBs also block calcium going into the conducting cells in the heart and have the added effect of slowing the heart rate.

Fast facts

  • Calcium channel blockers (CCBs) are commonly prescribed to treat high blood pressure and angina
  • There are two classes of CCBs: dihydropyridines and non-dihydropyridines
  • Serious side effects are rare

What are the different types?

There are two distinct chemical classes of CCBs: the dihydropyridines (such as nifedipine and amlodipine) and the nondihydropyridines (diltiazem and verapamil). The two classes both help to relax and widen arteries but non-dihydropyridines have an additional effect on the heart’s conduction system and can help to control certain fast heart rhythms (such as atrial fibrillation). This is because non-dihydropyridines also block calcium going into the conducting cells in the heart, which has the effect of slowing down the heart rate.

What medications are commonly prescribed alongside CCBs?

For most people who take CCBs, serious side effects are rare

If you need more than one blood-pressure-lowering drug, a CCB is often combined with an ACE inhibitor or diuretic. If you’ve been prescribed a CCB for angina, you may also receive other medications to help control your symptoms.

What are the possible side effects?

For most people who take CCBs, serious side effects are rare. The most common side effects of the dihydropyridine CCBs are ankle swelling, flushing and palpitations. The non-dihyropyridines, especially verapamil, can cause constipation and may slow your heart rate. Both classes of CCBs may also cause your blood pressure to drop excessively, which can result in dizziness. If you experience any symptoms, talk to your GP as soon as possible. Don’t stop taking your CCB without discussing it as it could result in a flare-up of your angina.

If I experience side effects, is there an alternative medication I can take?

ACE inhibitors, sartans, alpha-blockers and thiazide diuretics are all possible alternatives. Your doctor can discuss the best option for you.

Are there any foods I should avoid when taking CCBs?

Regular physical activity can help to reduce and control your blood pressure

Despite their name, CCBs can be safely taken with oral calcium supplements that may be prescribed to prevent or treat osteoporosis. Drinking grapefruit juice is not recommended and can, with some CCBs (nifedipine, diltiazem and verapamil), increase the risk of side effects. The herbal extract St John’s wort can make CCBs less effective so is also not recommended. Read the instructions on your medication carefully and discuss any concerns with your GP or pharmacist.

What else can I do to lower my blood pressure?

Regular moderate-intensity physical activity can help to reduce and control your blood pressure, and you should aim to do a minimum of 150 minutes a week. People who have a lot of salt in their diet are also more likely to have high blood pressure and most people eat far more than they need. You should have no more than 6g (about 1 tsp) of salt a day. Check food labels and watch out for processed foods because they often contain a lot of salt.

Maintaining a healthy weight can also help protect you against high blood pressure. If you smoke, it’s important to stop. Stopping smoking is the single most important thing you can do for your heart health.

Learn more about medications for your heart

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