Calcicard CR (Diltiazem)

How does it work?

Calcicard CR tablets contain the active ingredient diltiazem, which is a type of medicine called a calcium-channel blocker. This type of medicine acts on the heart and blood vessels.

Diltiazem works by slowing down the movement of calcium through muscle cells that are found in the heart and the walls of blood vessels. It does this by blocking 'calcium channels' on these muscle cells. Calcium is needed by the muscle cells in order for them to contract. By depriving them of calcium, diltiazem causes the muscle cells to relax. This action of diltiazem has two main effects; it slows down the rate at which the heart beats and it allows the blood vessels in the body to widen.

When the heart beats more slowly, the pressure at which the blood is pumped out of the heart is reduced. When the blood vessels in the body relax and widen, this decreases the resistance that the heart has to push against in order to pump the blood around the body. Both these actions reduce the pressure within the blood vessels. This means diltiazem can be used to lower high blood pressure.

Slowing the heart rate also reduces the energy used by the heart to pump blood around the body. This in turn reduces the heart's need for oxygen. At the same time, widening the blood vessels improves the blood and therefore oxygen supply to the heart. Both these features mean that diltiazem can be used in the management of angina.

The chest pain of angina is caused by insufficient oxygen supply to the heart. As diltiazem improves this oxygen supply, and also reduces the effort the heart has to make to pump blood, it can be used to prevent angina attacks.

Calcicard CR tablets are a long-acting or 'slow-release' form of diltiazem. They are designed to release the diltiazem slowly and continuously over 12 hours to help produce a steady blood level of the medicine throughout the day.

What is it used for?

  • Angina pectoris (as a regular treatment to help prevent attacks).
  • Mild to moderate high blood pressure (hypertension).

How do I take it?

  • Calcicard CR tablets are designed to be taken twice a day (every 12 hours). The dose prescribed will depend on the condition being treated. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label your pharmacist has put on the packet of medicine.
  • The tablets can be taken with or without food.
  • The tablets should be swallowed whole with a drink of water. They should not be broken, crushed or chewed, as this would damage the slow-release action and cause all the medicine to be released at once, which could be potentially dangerous.


  • Blood pressure lowering medicines can occasionally make you feel dizzy or weary. If you are affected, you should take care when driving or operating machinery.
  • If you experience any chest pain after taking this medicine you should not take a further dose until you have consulted your doctor.
  • This medicine must not be used to treat an attack of angina, as it won't work quickly enough.
  • There are several different brands of long-acting or modified-release diltiazem available in the UK (see end of factsheet). These can usually be identified because their names end in XL, MR, LA, SR and so on. The way that the diltiazem is released from different brands can vary and this means that different brands can have different clinical effects. For this reason, it is important that you always take the same brand of diltiazem. You should make sure you know which brand you take and check that you have been given the correct one each time your medicine is dispensed. (Your pharmacist will usually ask you, or call your doctor if this is not written on your prescription).

Use with caution in

  • Elderly people.
  • Decreased kidney function.
  • Decreased liver function.
  • People with slowed conduction of electrical messages between the chambers of the heart (1st degree heart block).
  • People with a slow heart rate (bradycardia).
  • Heart failure.
  • People with an abnormal heart rhythm seen as a 'prolonged PR interval' on a heart monitoring trace (ECG).

Not to be used in

  • People with a serious defect in the heart's electrical message pathways, resulting in decreased function of the heart (2nd or 3rd degree heart block).
  • A problem called sick sinus syndrome, which is common in elderly people and is related to poor control of the working of the heart.
  • People with poor functioning of one chamber of the heart (left ventricular dysfunction), resulting in fluid build-up in the lungs.
  • Uncontrolled heart failure.
  • People with a very slow heart rate (less than 40 beats per minute).
  • Pregnancy.
  • Breastfeeding.
  • Hereditary blood disorders called porphyrias.
  • This medicine is not recommended for children.
  • People with rare hereditary problems of fructose or galactose intolerance, the Lapp lactase deficiency, sucrase-isomaltase insufficiency or glucose-galactose malabsorption (Calcicard CR tablets contain sucrose and lactose).

This medicine should not be used if you are allergic to one of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine should not be used during pregnancy. Seek further medical advice from your doctor.
  • This medicine passes into breast milk in amounts that are probably too small to be harmful to the nursing infant. However, since the medicine does pass into breast milk, the manufacturer recommends that it should not be used by breastfeeding mothers. Seek medical advice from your doctor.

Label warnings

  • This medication is to be swallowed whole, not chewed.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Swollen ankles caused by fluid retention (peripheral oedema).

Common (affect between 1 in 10 and 1 in 100 people)

  • Headache.
  • Dizziness.
  • Flushing.
  • Disturbances of the gut, such as constipation, indigestion, nausea, abdominal pain.
  • Feeling weak.
  • Fatigue.
  • Redness of skin.

Uncommon (affect between 1 in 100 and 1 in 1000 people)

  • Nervousness.
  • Difficulty sleeping.
  • Slower than normal heart beat (bradycardia).
  • A drop in blood pressure that occurs when moving from a lying or sitting position to sitting or standing, causing dizziness and lightheadedness (postural hypotension).
  • Diarrhoea.
  • Vomiting.
  • Elevation in levels of liver enzymes.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Dry mouth.
  • Hive like rash (urticaria).

Unknown frequency

  • Abnormal enlargement of the breasts in men (gynaecomastia).
  • Changes in mood including depression.
  • Reversible enlargement of the gums (gingival hyperplasia) with long-term use.
  • Inflammation of the liver (hepatitis).
  • Low blood pressure (hypotension).
  • Increased sweating.
  • Abnormal reaction of the skin to light, usually a rash (photosensitivity).
  • Severe skin reactions.
  • Decrease in the number of platelets in the blood (thrombocytopenia).
  • Blockade of the electrical pathways which control the pumping action of the heart (heart block).
  • Heart failure.
  • Inflammation of blood vessels (vasculitis).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Likewise, always ask your doctor or pharmacist before taking any new medicines during treatment with this one, to check that the combination is safe.

If diltiazem is used in combination with other medicines that lower blood pressure, either to treat high blood pressure (antihypertensives), or as a side effect, the combination might lower your blood pressure too much. This could make you feel dizzy or faint, particularly when moving from a lying or sitting position to sitting or standing. This is more likely when you first start taking diltiazem with one of these medicines. If you feel dizzy or faint you should sit or lie down until the symptoms pass. Tell your doctor if any dizziness persists, as your medicine doses may need adjusting. Other medicines that decrease blood pressure include the following:

  • ACE inhibitors, eg enalapril
  • aldesleukin
  • alpha-blockers such as prazosin
  • alprostadil
  • angiotensin II receptor antagonists such as losartan
  • antipsychotics
  • beta-blockers such as propranolol
  • baclofen
  • benzodiazepines, eg temazepam, diazepam
  • other calcium-channel blockers, eg verapamil, nifedipine
  • clonidine
  • diazoxide
  • diuretics, eg furosemide, bendroflumethiazide
  • dopamine agonists, eg bromocriptine, apomorphine
  • MAOI antidepressants, eg phenelzine
  • methyldopa
  • minoxidil
  • moxisylyte
  • moxonidine
  • nicorandil
  • nitrates, eg glyceryl trinitrate
  • tizanidine
  • vardenafil.

There may be an increased risk of a slowed heart rate and heart block if amiodarone, beta-blockers (for example atenolol, propranolol, timolol) or dronedarone are used in combination with diltiazem

The following medicines may increase the breakdown of diltiazem by the liver and could therefore make it less effective. If you take any of these in combination with diltiazem your doctor may need to increase your diltiazem dose:

  • efavirenz
  • phenobarbital
  • phenytoin
  • primidone
  • rifampicin
  • the herbal remedy St John's wort (Hypericum perforatum).

The following medicines may decrease the breakdown of diltiazem by the liver and may therefore increase the amount of diltiazem in the blood. If you take any of these in combination with diltiazem your doctor may need to lower your diltiazem dose:

  • H2 antagonists such as cimetidine, ranitidine
  • protease inhibitors for HIV infection such as atazanavir or ritonavir.

Diltiazem may decrease the breakdown of the following medicines by the liver and may therefore increase the amount of these medicines in the blood. As this could increase the risk of their side effects, your doctor may need to prescribe a lower dose of these medicines if you take them in combination with diltiazem:

  • aprepitant
  • atorvastatin
  • buspirone
  • carbamazepine
  • ciclosporin
  • cilostazol
  • colchicine
  • digoxin
  • eplerenone
  • ivabradine (should not be used with diltiazem)
  • methylprednisolone
  • midazolam
  • nifedipine (nifedipine also increases the blood level of diltiazem)
  • phenytoin
  • ranolazine
  • quinidine
  • simvastatin
  • sirolimus
  • tacrolimus
  • theophylline
  • triazolam
  • tricyclic antidepressants such as imipramine.

If diltiazem is taken in combination with lithium there may be an increased risk of lithium side effects. If you take these medicines together it is important to tell your doctor if you experience any new or increased signs of lithium side effects.

The following medicines may reduce the blood pressure lowering effect of this medicine:

  • corticosteroids, such as dexamethasone or prednisolone
  • oestrogens, such as those in the contraceptive pill
  • regular use of non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac or indometacin (occasional painkilling doses are unlikely to have a significant effect).

Dantrolene infusion should not be given to people taking diltiazem.

Other medicines containing the same active ingredient

Adizem-SR Adizem-XL Angitil SR
Angitil XL Dilcardia SR Dilzem SR
Dilzem XL Slozem Tildiem
Tildiem LA Tildiem Retard Viazem XL
Zemtard XL

Short-acting diltiazem tablets are also available without a brand name, ie as the generic medicine.