Dose and administration
The emergency dose of adrenaline is 0.01 mg/kg of a 1 mg/mL (1:1000) dilution to a maximum dose of 0.5 mg in an adult and 0.3 mg in a child.
Adrenaline can be given intramuscularly (IM), intravenously (IV) or subcutaneously (SC). However, IV administration must be given by a healthcare professional; in practice adrenaline is generally given by the IM route using an auto-injector, such as EpiPen® (adrenaline) auto-injector, as it is more quickly absorbed than when given by SC injection. This is an important consideration because rapid absorption of adrenaline is critical to reversing the symptoms of anaphylaxis.
Up to 35% of patients need more than one dose of adrenaline to reverse anaphylaxis symptoms. Specifically, in one retrospective review, 65% of patients needed 1 dose; patients with more severe symptoms required more than one injection twice as often as those with milder symptoms.40 It may therefore be advisable for patients to routinely carry two auto-injectors with them at all times in order to be prepared for administration of a second dose if required to combat the initial anaphylactic response.
Adrenaline can be re-injected every 5 to 15 minutes until there is resolution of anaphylaxis or signs of adrenaline toxicity occur (e.g. palpitations, tremor, uncomfortable apprehension and anxiety).41 It is important to note that the patient should administer no more than two doses, any further doses must be given by a healthcare professional.
Additionally, as many as 20% of patients will go on to develop a second anaphylactic response (see biphasic response in Mechanisms) many hours later. The second phase usually occurs after an asymptomatic period of 1 to 72 hours, but most occur within 8 hours after the initial reaction.20 About one third of the second-phase reactions are more severe, one third are as severe, and one third are less severe and so patients should be observed for at least 6 hours after the initial symptoms of anaphylaxis subside, and maybe for 12 hours if considered appropriate.25,22
- 20 - Kemp SF et al. World Allergy Org J 2008;1(7):S18-S26.
- 22 - NICE clinical Guideline. Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after emergency treatment for a suspected anaphylactic episode Draft for consultation, July 2011
- 25 - Resuscitation Council (UK) Guidelines. January 2008. Available at: www.resus.org.uk/pages/reaction.pdf Accessed on 03 June 2011.
- 40 - Korenblat P et al. Allergy Asthma Proc. 1999;20(6):383-386
- 41 - EpiPen Summary of Product Characteristics, MEDA Pharmaceutical Ltd, April 2011.