Adrenaline (epinephrine) is the emergency treatment for a serious allergic reaction. If it’s given quickly, it can treat the features of anaphylaxis by acting on adrenoceptors.
As an alpha-receptor agonist, it reverses vasodilatation and reduces oedema.
As a beta-receptor, it dilates the airways, increases the force of myocardial contraction, and suppresses further histamine and leukotriene release.
Who Needs to be Prescribed Adrenaline?
Allergic reactions vary in severity. In its 2016 guidelines, the British Society of Allergy and Clinical Immunology (BSACI) suggests that people who should be considered for long-term provision of an adrenaline auto-injector include those:
...who have suffered an anaphylactic reaction where the cause is unknown (idiopathic anaphylaxis)
...who have suffered an anaphylactic reaction where the known allergic trigger cannot easily be avoided
...who are allergic to high-risk allergic triggers, for example nuts, with other risk factors also present, such as asthma, even if the reaction was relatively mild
...who had a reaction in response to trace amounts of the allergic trigger
...where an anaphylactic reaction triggered by food is only likely to occur if that food is eaten around the time of physical exercise (known as Food-Dependant Exercise-Induced Anaphylaxis or FDEIA).
...where other significant risk factors are present (such as asthma in someone with a food allergy).
Because the course of serious allergic reactions is varied and unpredictable, it is difficult to define when adrenaline is best administered. The UK Resuscitation Council recommends giving adrenaline as soon as there is stridor (noisy breathing), respiratory distress, wheezing or clinical signs of shock. Urgent transfer to hospital is vital.
Adverse Effects of Adrenaline & Drug Interactions
Unwanted effects are rare when appropriate doses of adrenaline are given. However, prescribers should consider all co-existing medical conditions and check for potential interactions. For example, beta-blockers and ACE inhibitors may hinder treatment.
When prescribing medicines for people with food allergies, check the ingredients and excipients to ensure the food allergens they react to are not present.
Replacing Adrenaline Auto-Injectors
Adrenaline injectors have expiry dates and may be less effective after that date. Therefore, it is helpful to do a regular audit of prescribed adrenaline to identify patients whose last prescription was more than two years ago. The MHRA have also produced an infographic to give to patients, and manufacturers have an expiry alert service.