Verapamil - a calcium-channel blocker

About verapamil

Verapamil is known as a calcium-channel blocker because it works by affecting the way calcium passes into certain muscle cells. It is prescribed to treat a number of heart and blood vessel-related conditions. These are abnormal heart rhythms (arrhythmias), high blood pressure (hypertension), and angina chest pain.

Your heart and the walls of your arteries contain special muscle cells. These muscle cells need calcium to contract. Verapamil reduces the amount of calcium that goes into these muscle cells. This causes the muscle cells to relax which widens your arteries and reduces the force and rate of your heartbeat. Opening up your arteries lowers your blood pressure and increases the flow of blood to your heart, which helps ease angina. Because verapamil blocks calcium going into special conducting cells in your heart, it is used to treat certain arrhythmias where the heart rate is abnormally fast.

Verapamil has also been found helpful in preventing migraine headaches in some people. This leaflet does not contain information about this, but your doctor can give you more information if you have been prescribed it for this reason.

Before taking verapamil

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking verapamil it is important that your doctor knows:

• If you are pregnant, trying for a baby or breastfeeding.
• If you have been told you have a condition where the pumping action of your heart is reduced (heart failure), or any other heart condition.
• If you have low blood pressure (hypotension).
• If you have any problems with the way your liver works.
• If you have a rare inherited blood disorder called porphyria.
• If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines. It is particularly important that your doctor knows if you are taking a beta-adrenoceptor blocking drug (commonly known as a beta-blocker).
• If you have ever had an allergic reaction to a medicine.

How to take verapamil

• Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. It will give you more information about the brand of verapamil your doctor has prescribed for you. It will also provide you with a full list of the side-effects which you may experience from taking verapamil.
• Take verapamil exactly as your doctor tells you to. You may be asked to take verapamil once, twice or three times a day depending on the preparation you are given. Your doctor or pharmacist will tell you what dose is right for you. The dose will also be printed on the label of the pack to remind you about what your doctor said to you.
• Swallow the tablet/capsule with a drink of water. You can take verapamil either before or after a meal.
• Try to take your doses of verapamil at the same times of day, each day. Having a routine will help you to remember to take your doses regularly.
• Prolonged-release (also called modified-release) forms of verapamil have been made to release verapamil slowly, to give a more even effect throughout the day. These forms of tablets/capsules should not be chewed, sucked or crushed, otherwise you could receive too much verapamil too quickly. The label on the pack of tablets/capsules you receive will give you information about this.
• If you forget to take a dose, take it as soon as you remember, unless it is nearly time for your next dose, in which case leave out the missed dose. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

• Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress.
• It is not advisable for you to drink grapefruit juice while you are on verapamil. This is because a chemical in grapefruit juice increases the amount of verapamil in your bloodstream and this increases the risk of side-effects.
• If you drink alcohol, ask your doctor for advice. Your doctor may recommend that you do not drink alcohol while you are on this medicine, as there is an increased risk that you will experience side-effects. Also, the level of alcohol in your blood may be increased by verapamil.
• If you buy any medicines, always check with a pharmacist that they are suitable to take with your other medicines. Some anti-inflammatory painkillers and the herbal remedy called St John's wort can interfere with verapamil.
• If you need to have an operation or any medical treatment, always tell the person carrying out the treatment which medicines you are taking. Verapamil and some anaesthetics can interact, meaning that unwanted effects can be more likely.

Can verapamil cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with verapamil. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

If you experience any other symptoms which you think may be due to verapamil, speak with your doctor or pharmacist for further advice.

How to store verapamil

• Keep all medicines out of the reach and sight of children.
• Store in a cool, dry place, away from direct heat and light.

Important information about all medicines