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