Adenosine (Adenocor injection)

How does it work?

Adenocor injection contains the active ingredient adenosine, which is a type of medicine called an anti-arrhythmic. Adenosine is also available without a brand name, ie as the generic medicine. Adenosine is a natural body chemical that is used to control abnormal heartbeats.

The heart's pumping action is controlled by electrical signals that pass through the heart muscle. The electrical signals cause the two pairs of heart chambers (left and right atria and ventricles) to contract in a regular manner that produces the heartbeat. If the electrical activity in the heart is disturbed for any reason, irregular heartbeats (arrhythmias) of various types can result. These can seriously undermine the pumping action of the heart and result in inefficient blood circulation around the body.

Electrical impulses start in a part of the heart called the sinoatrial node and then spread over the atria (upper chambers of the heart), causing them to contract. The impulses then pass through the atrio-ventricular node (AV-node) to the ventricles (lower chambers of the heart). The impulse spreads over the ventricles, causing them to contract and pump blood out to the rest of the body.

Adenosine is used to treat abnormal heart rhythms where the heart sporadically beats very rapidly, as a result of problems with the electrical message pathways in the top part of the heart (paroxysmal supraventricular tachycardia). It controls this type of arrhythmia by slowing the conduction of electrical impulses across the AV node. This quickly (within a few minutes) causes the heart to return to its normal rhythm.

What is it used for?

  • Correcting an abnormal heart rhythm where the heart sporadically beats very rapidly, as a result of problems with the electrical message pathways in the top part of the heart (paroxysmal supraventricular tachycardia). This may be associated with conditions such as Wolff-Parkinson-White syndrome.
  • Aiding diagnosis of the type of irregular heartbeat.

How is this medicine given?

  • Adenosine is given as a rapid injection into a vein (intravenously). Your heart will be monitored with an ECG while the medicine is being administered.
  • Food and drinks containing caffeine such as tea, coffee, chocolate and cola should be avoided for at least 12 hours before you are given Adenocor injection.

Use with caution in

  • People who have recently had a heart attack (myocardial infarction).
  • People with heart failure.
  • People with minor problems with the conduction of electrical messages between the chambers of the heart (1st degree heart block or bundle branch block).
  • People with a type of irregular heartbeat called atrial flutter or atrial fibrillation.
  • People with an abnormal heart rhythm seen on a heart monitoring trace (ECG) as a 'prolonged QT interval'.
  • People who have a left-right shunt in the heart - blood goes directly from the left side of your heart to the right side.
  • People with narrowing of the main left side artery in the heart (left main coronary stenosis).
  • People with heart disease caused by narrowing of the heart valves (heart valve stenosis).
  • People with inflammation around the heart (pericarditis) or leaking of fluid into the sac surrounding the heart (pericardial effusion).
  • People who have had a heart transplant in the last year.
  • People with low levels of fluid in their blood (hypovolaemia).
  • People with a history of convulsions or fits, eg epilepsy.
  • People with narrowing of the main arteries in the neck (carotid arteries), causing poor blood circulation to the brain (cerebrovascular insufficiency).
  • People who have problems with the autonomic nervous system (this is the part of the nervous system that allows the body to carry out its normal day to day functioning - it is not under voluntary control).
  • People on a low sodium diet (this medicine contains sodium).

Not to be used in

  • A problem called sick sinus syndrome, which is common in elderly people and is related to poor control of the working of the heart (although this medicine may be used in people with this condition who have an artificial pacemaker fitted).
  • 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), unless an artificial pacemaker is fitted.
  • People with an abnormal heart rhythm called 'long QT syndrome'.
  • Uncontrolled heart failure.
  • People with very low blood pressure (severe hypotension).
  • People with lung problems such as asthma or COPD.

This medicine should not be used if you are allergic to any 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, inform your doctor 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.

  • The safety of this medicine for use in pregnancy has not been established. It should be used with caution during pregnancy and only if the potential benefits outweigh any possible risks to the developing baby.
  • It is not known if this medicine passes into breast milk, however, this is unlikely because the medicine only stays in the body for a few seconds. The manufacturer states that this medicine should not be used during breastfeeding. Seek medical advice from your doctor.

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, it 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)

  • Slow heart rate (bradycardia).
  • Skipped heartbeats or extra heartbeats.
  • Problems with the electrical message pathways in the heart (atrioventricular block).
  • Increased blood flow to the skin (flushing).
  • Shortness of breath or the urge to take a deep breath (dyspnoea).
  • Feeling of chest pain or pressure on the chest.

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

  • Nausea.
  • Headache.
  • Dizziness.
  • Lightheadedness.
  • Burning sensation.
  • Feeling of apprehension.

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

  • Blurred vision.
  • Metallic taste.
  • Fast breathing (hyperventilation).
  • Awareness of your heartbeat (palpitations).
  • Increased heart rate.
  • Sweating.
  • Feeling of pressure in the head.
  • Feeling of general discomfort, weakness or pain.

Very rare (affect less than 1 in 10,000 people)

  • Reaction at the site of injection.
  • Very slow heart rate (severe bradycardia).
  • Other types of irregular heartbeat.
  • Breathing difficulties due to a narrowing of the airways (bronchospasm).

Frequency unknown

  • Vomiting.
  • Low blood pressure, sometimes severe.
  • The heart stops beating (asystole or cardiac arrest).
  • Breathing slows down or stops (respiratory failure or arrest).
  • Fainting.
  • Loss of consciousness.
  • Convulsions.

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 already taking, including those bought without a prescription and herbal medicines, before you have treatment with this medicine, so they can make sure that the combination is safe.

There may be an increased risk of the heart beating too slowly if the following medicines are used in combination with adenosine:

  • beta-blockers such as atenolol, propranolol
  • calcium-channel blockers such as verapamil
  • local anaesthetics such as bupivacaine , levobupivacaine, prilocaine or ropivacaine
  • other anti-arrhythmic medicines such as dipyridamole.

Dipyridamole can significantly enhance the effect of adenosine. The manufacturers advise that adenosine should not be given to people taking dipyridamole unless absolutely necessary. In this case, the dipyridamole should be stopped 24 hours before the adenosine is given, or a much lower dose of adenosine should be used.

Theophylline or aminophylline may oppose the therapeutic effect of adenosine, so these medicines should not be given for at least 24 hours before an adenosine injection.

Other medicines containing the same active ingredient

  • Adenoscan.

Adenosine injections are also available generically (ie without a brand name).