Intramuscular adrenaline is the first line treatment for anaphylaxis.1

Severe allergic reactions can occur in response to food, insect stings, medication, latex, exercise and other allergens.

Adrenaline must be administered to patients experiencing anaphylaxis and to patients with clinical features that are likely to evolve into anaphylaxis.1

Symptoms of anaphylaxis include the following:1

  • AIRWAY – Persistent cough, hoarse voice, difficulty swallowing, swollen tongue
  • BREATHING – Difficult or noisy breathing, wheeze or persistent cough
  • CIRCULATION – Persistent dizziness, pale or floppy, suddenly sleepy, collapse/unconscious

Adrenaline MOA

ADRENALINE

Smooth muscle contraction and increased vascular resistance

Smooth muscle contraction and inhibition of transmitter release

Increases cardiac contraction force and increases heart rate

Decreases mediator release and increase bronchodilation

Increased blood pressure and decreased mucosal oedema

Increased blood pressure and relief from shock. Decreased upper airway obstruction, wheezing, urticaria and angioedema

Smooth muscle contraction and increased vascular resistance

Smooth muscle contraction and inhibition of transmitter release

Increases cardiac contraction force and increases heart rate

Decreases mediator release and increase bronchodilation

Increased blood pressure and decreased mucosal oedema

Increased blood pressure and relief from shock. Decreased upper airway obstruction, wheezing, urticaria and angioedema

Adrenaline acts swiftly to reverse the symptoms of anaphylaxis. It opens up the airways by reducing swelling and increasing blood pressure.2

Adrenaline has a vasodilator effect in skeletal muscle, skeletal muscle is well vascularised; after intramuscular injection into the vastus lateralis (mid-anterolateral thigh), absorption is rapid and adrenaline reaches the central circulation rapidly; rapid absorption is important in anaphylaxis, in which the median times to cardiorespiratory arrest are reported as 5 minutes iatrogenic (injected medication), 15 minutes (stinging insect venom), 30 minutes (food).3

EAACI anaphylaxis guidelines recommend the following doses of adrenaline for self-administration, to be given by intramuscular injection.1

  • For adult and child body weight 25kg and above - 0.3mg
  • For child body weight 7.5 kg- 25kg - 0.15mg

Adrenaline auto-injectors are prescribed for self-administration and should be administered as soon as anaphylaxis is identified. It is possible that a biphasic reaction may occur, which is one of the reasons why guidelines state that patients should be prescribed 2 adrenaline auto-injectors which they should carry at all times.4

References

  1. Muraro A, et al. EAACI guidelines: Anaphylaxis. 2022;77: 357-377
  2. Anaphylaxis UK. Available at: https://www.anaphylaxis.org.uk/fact-sheet/adrenaline/. Last accessed: May 2023
  3. Simons, F.E.R., 2011. World allergy organization guidelines for the assessment and management of anaphylaxis. World Allergy Organization Journal, 4(2), pp.13-37.
  4. MHRA Advice. Available at: https://www.gov.uk/drug-safety-update/adrenaline-auto-injectors-updated-advice-after-european-review. Last accessed: May 2023