What are the 'ideal' features of an adrenaline (epinephrine) auto-injector in the treatment of anaphylaxis?

Anaphylaxis is a systemic allergic reaction that often involves respiratory symptoms and cardiovascular collapse, which are potentially life-threatening if not treated promptly with intramuscular adrenaline. Owing to the unpredictable nature of anaphylaxis and accidental exposure to allergens (such as peanuts and shellfish), patients should be prescribed intramuscular adrenaline auto-injectors and carry these with them at all times. Patients also need to be able to use their auto-injectors correctly while under high stress, when an anaphylactic attack occurs. Despite this, an alarming number of patients fail to carry their auto-injectors and many patients, carers of children with known anaphylaxis and healthcare professionals do not know how to use the device correctly, despite having had training. Currently available auto-injector devices have various limitations that may impede their use in the management of anaphylaxis. There is also a lack of validated assessment criteria and regulatory requirements for new devices. This review describes the different delivery systems used in currently available auto-injectors and discusses the key barriers to the use of adrenaline auto-injectors, with the goal of identifying the 'ideal' features/characteristics of such devices in the emergency treatment of anaphylaxis that will ensure ease of use, portability and accurate delivery of a life-saving drug.