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Calcium-channel blockers are a type of medication that is commonly used to treat high blood pressure. They work by slowing down the speed with which calcium enters certain muscles in the body.
Blocking the action of calcium on the cells in your blood vessels mean that the blood vessels relax and stay more open. This allows blood to move more freely through your blood vessels, which lowers your blood pressure.
There are different types of calcium-channel blocker, but the most commonly used in the UK is a type called dihydropyridines.
Who should take calcium-channel blockers?
Calcium-channel blockers are often used in people who are aged older than 55 years old and for people who are of African-Caribbean descent (but not mixed race). This is because research has shown that this group of medicines is most effective in these groups of people.
Who should not take calcium-channel blockers?
With the exception of nifedipine, calcium-channel blockers should not be taken if you are pregnant, trying to become pregnant, or breastfeeding, because they may affect your baby's development. Instead your doctor will prescribe one of the other types of blood pressure drug that will not cause any unwanted effects to the baby.
If you have heart failure, or enlargement of the left side of the heart, you will need to be monitored closely if you are taking calcium-channel blockers.
People with liver problems will also need to be monitored closely if they are taking calcium-channel blockers.
What are the most common side-effects of calcium-channel blockers?
Because calcium-channel blockers relax and widen your blood vessels, all of them can cause occasional headaches or flushing of your face. This often occurs for the first few days of taking the tablets and usually disappears.
Swollen ankles are also common, particularly at the end of a day when you have been standing for a while. This usually only occurs with higher doses of the medicine.
Constipation can occur, particularly with some types of calcium-channel blocker.
Dihydropyridines can cause side-effects such as ankle and foot pain, a rash on the lower part of the foot, or in men, a greater need to go to the toilet, particularly at night (this is called nocturia).
Other less common side-effects include: feeling sick, palpitations, tiredness and dizziness, or swelling and bleeding of the gums.
If you develop side-effects from your medications, your doctor may be able to help by lowering your dose, or by changing your medicine. Do not stop taking any medication without first speaking to your doctor.
Types of dihydropyridines
Most medications have two names – the generic name (which is the name of the medicine itself) and the brand name (which is the name the medicine is sold under). This means different companies may make and sell the same medicine, but they may sell it with different brand names. The table below lists some dihydropyridine calcium-channel blockers currently used in the UK:
| Generic name | Brand names |
| Amlodipine | Amlostine, Exforge, Istin |
| Felodopine | Felotens XL, Plendil, Triapin, Triapin Mite, Vascalpha |
| Isradipine | Prescal |
| Lacidipine | Motens |
| Lercanidipine | Zanidip |
| Nicardipine | Cardene |
| Nifedipine | Adalat, Adalat LA, Adalat Retard, Beta-Adalat, Coracten SR, Coracten XL, Nifedipress, Tenif, Tensipine |
| Nisoldipine | Syscor |
Other types of calcium-channel blockers
Although dihydropyridines are the most commonly-used calcium-channel blockers in the UK, there are others available. They include:
Verapamil: this medicine works in the same way to lower high blood pressure as dihydropyridines but it also slows the heart rate and is less likely to cause swelling of the ankles and nocturia. Because of its effects on the heart rate, it is also used to treat angina and certain irregular heart rhythms. If you have just had a heart attack, you should be monitored closely if you are taking verapamil. If you are already taking a beta-blocker, you should not take verapamil.
Verapamil is available under different brand names, including: Securon SR, Tarka, Univer, Verapamil, Verapress.
Diltiazem: this medicine is not commonly used in the UK. It works similarly to the others but is less likely to cause side-effects like ankle swelling or constipation. If you have heart failure or some types of irregular heart rhythm, you should be monitored closely if you are taking diltiazem.
Diltiazem is available under different brand names, including: Adizen-SR, Adizem-XL, Diltiazem, Dilzem SR, Dilzem XL, Slozem, Tildiem, Tildiem LA, Tildiem Retard, Viazem XL.
Other things you need to know
If you are taking calcium-channel blockers, then you should not drink grapefruit juice. It increases the amount of medication that enters your bloodstream, and can therefore be dangerous. Apart from amlodipine and diltiazem, almost all calcium-channel blockers are affected by grapefruit juice. The juice from oranges and other citrus fruits is considered safe.
Some people with chest pain (angina) can have a flare up of their chest pain if they stop taking their calcium-channel blocker suddenly. So do not to stop taking these tablets without first talking to your doctor.
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