Adrenaline (Anapen)

How does it work?

Anapen and Anapen Junior injections both contain the active ingredient adrenaline, which is a hormone produced naturally by the body. It is given by injection to treat a life-threatening allergic reaction called anaphylactic shock. (NB. Adrenaline is also sometimes referred to as epinephrine.)

Adrenaline is released by the adrenal glands in times of stress. It prepares the body when extra energy or exertion is needed, making the body more able to deal with life-threatening situations.

Anaphylatic shock is a severe allergic reaction that can be triggered by a drug or food allergy, or by an insect bite. A severe reaction of this type can include the following symptoms: itching of the skin, a raised rash (like a nettle rash), swelling of your lips, tongue, throat, hands and feet, flushing, weak pulse, tightening of the chest, difficulty in breathing, fall in blood pressure and in some cases loss of consciousness.

Adrenaline reverses the symptoms of anaphylaxis by acting on alpha and beta adrenergic receptors in the body.

Alpha receptors are found on the walls of blood vessels. When adrenaline stimulates these receptors this causes the blood vessels to narrow, which stops the blood pressure from falling too low. It also redirects blood to vital organs like the heart and brain.

Beta receptors are found in the heart and lungs. When adrenaline stimulates these receptors this relaxes and opens the airways, making breathing easier. It also stimulates the heart, making it beat faster and stronger.

Adrenaline also relieves itching, hives and swelling.

Anapen injections are prescribed to people who have a history or recognised risk of going into anaphylactic shock due to an allergy. The Anapen is intended for self-administration in an emergency and should be carried with you at all times.

The Anapen is designed to be used by people with no medical training. Your doctor will teach you how and when to use it. First you need to remove the black needle cap that covers the needle and the black safety cap that covers the red firing button. The Anapen should then be held against the outer thigh while you press the red firing button. This pushes the hidden needle into the thigh muscle and delivers a dose of adrenaline. The pen should be held firmly in the thigh for 10 seconds. The Anapen can be injected through clothes.

What is it used for?

  • Emergency treatment of life-threatening allergic reactions (anaphylactic reactions) for example to food, drugs or insect bites or stings.

The Anapen is designed as emergency treatment only. You should always seek medical help immediately after using it in case further treatment is needed.


  • This medicine must only be used to treat anaphylaxis in people who have been prescribed the Anapen by their doctor. This will be because they have a history or recognised risk of going into anaphylactic shock. The Anapen should not be used to treat anyone else, even if they have similar symptoms.
  • It is very important to use the Anapen only as instructed by your doctor. You should make sure that you understand exactly WHEN and HOW to use the Anapen. If you are at all unclear about when or how to use the injection you should ask your doctor or pharmacist to explain the instructions again so that you know what to do in an emergency.
  • Anapen injections should ONLY be injected into the outer side of the thigh. Do NOT inject into a vein, or into the buttock, as this may accidentally inject into a vein.
  • If the Anapen injection is accidentally injected into the hands, fingers or feet it may result in loss of blood flow to this area. If you do accidentally inject it into one of these areas then emergency medical treatment should be sought immediately.
  • You should check the expiry date on your Anapen injection from time to time to make sure that it is still in date. If it is due to expire you should consult your doctor for a new prescription and return the expired Anapen to your pharmacist.

Use with caution in

  • Heart disease.
  • Irregular heart beats (arrhythmias).
  • High blood pressure (hypertension).
  • Overactive thyroid gland (hyperthyroidism).
  • Tumour of the adrenal gland (phaeochromocytoma).
  • Diabetes.
  • People with raised pressure in the eyeball, eg glaucoma.
  • Elderly people.
  • Pregnancy.
  • Allergy to sodium metabisulphite, which is used as a preservative in this product.

Not to be used in

  • There are no known conditions in which Anapen should not be used to treat an allergic emergency.
  • The injection should be administered into the outer thigh only. Make sure you don't accidentally inject it into the buttock, or into the hands or fingers (see warning above).

This medicine should not be used if you are allergic to one or 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, 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.

  • It is very important that you fully understand in which situations to use this medicine if you are pregnant. It should only be used if the benefits outweigh any risks to the baby. However, in an emergency you should not hesitate to use this medicine, since anaphylaxis can be life-threatening for you and your baby. Seek further medical advice from your doctor.
  • In an emergency you should not hesitate to use this medicine if you are breastfeeding, since anaphylaxis can be life-threatening. Any adrenaline that passes into breast milk is not expected to have any effect on a nursing infant, because adrenaline is not absorbed when taken by mouth. Seek further 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 does not mean that all people using this medicine will experience that or any side effect.

  • Headache.
  • Faster than normal heart beat (tachycardia).
  • Difficulties with breathing.
  • Shaking, usually of the hands (tremor).
  • Anxiety and nervousness.
  • Sweating.
  • Abnormal heart beats (arrhythmias).
  • Paleness.
  • Awareness of your heartbeat (palpitations).
  • Dizziness.
  • Feeling weak.
  • Nausea and vomiting.

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, when you are prescribed this medicine, so they can check that the combination is safe.

There may be an increased risk of side effects on the heart if this injection is used by people taking any of the following medicines:

  • beta-blockers eg propranolol
  • digoxin
  • entacapone
  • MAOI antidepressants, eg phenelzine
  • quinidine
  • tricyclic antidepressants, eg amitriptyline.

Adrenaline can decrease the amount of insulin produced by the body; this can cause an increase in blood sugar levels. People with diabetes should therefore carefully monitor their blood sugar after using this medicine.

Other medicines containing the same active ingredient