Bioavailability and cardiovascular effects of adrenaline administered by Anapen 500 μg auto-injector in healthy volunteers

Adrenaline Auto-Injectors for Preventing Fatal Anaphylaxis

Anaphylaxis affects up to 5% of people during their lifetime. Although anaphylaxis usually resolves without long-term physical consequences, it can result in anxiety and quality of life impairment. Rarely and unpredictably, community anaphylaxis can cause rapid physiological decompensation and death. Adrenaline (epinephrine) is the cornerstone of anaphylaxis treatment, and provision of adrenaline autoinjectors (AAI) has become a standard of care for people at risk of anaphylaxis in the community. In this article, we explore the effectiveness of AAIs for preventing fatal outcomes in anaphylaxis, using information drawn from animal and human in vivo studies and epidemiology. We find that data support the effectiveness of intravenous adrenaline infusions for reversing physiological features of anaphylaxis, typically at doses from 0.05 to 0.5 μg/kg/min for 1-2 h, or ~ 10 μg/kg total dose. Intramuscular injection of doses approximating 10 μg/kg in humans can result in similar peak plasma adrenaline levels to intravenous infusions, at 100-500 pg/mL. However, these levels are typically short-lived following intramuscular adrenaline, and pharmacokinetic and pharmacodynamic outcomes can be unpredictable. Epidemiological data do not support an association between increasing AAI prescriptions and reduced fatal anaphylaxis, although carriage and activation rates remain low. Taken together, these data suggest that current AAIs have little impact on rates of fatal anaphylaxis, perhaps due to a lack of sustained and sufficient plasma adrenaline concentration. Effects of AAI prescription on quality of life may be variable. There is a need to consider alternatives, which can safely deliver a sustained adrenaline infusion via an appropriate route.

Alternatives to Injectable Adrenaline for Treating Anaphylaxis

Adrenaline is the first line treatment for anaphylaxis and adrenaline auto-injectors (AAI) allow reliable, safe and ergonomic administration in the community. However, AAIs have significant limitations and adrenaline is often not used in anaphylaxis. Innovations to administer adrenaline via alternative routes may potentially improve usage rates and treatment effectiveness. Here, we describe the known limitations and barriers to AAI use in anaphylaxis. We then summarise current data for adrenaline devices which use alternative routes of administration for treating anaphylaxis. Several novel devices are in development, which deliver adrenaline via nasal, sublingual or transcutaneous routes. Pharmacokinetic, pharmacodynamic and safety studies have compared these treatments with AAI or intramuscular adrenaline via needle and syringe. The first non-injectable adrenaline delivery device for emergency treatment of anaphylaxis was approved in Europe and the United States. Neffy, an adrenaline nasal spray, is licensed for use in adult and paediatric patients who weigh at least 30 kg. In the near future, multiple alternatives to injectable adrenaline may be available for managing anaphylaxis, overcoming some, but not all of the limitations of AAIs.

Adrenaline auto injectors pharmacokinetic/pharmacodynamic studies and potential consequences for clinical practice

BACKGROUND

Anaphylaxis is a sudden multisystem allergic reaction which may result in a fatal outcome if not treated promptly. Guidelines worldwide suggest intramuscular adrenaline as the first-line treatment for anaphylaxis outside a perioperative reaction. Adrenaline autoinjectors (AAIs) are widely used self-administrable devices, especially in community settings. Different commercial AAIs have been authorized to be marketed in Europe. For an AAI to be efficacious, a rapid adrenaline delivery in patients, including those who are overweight or obese, resulting in an optimal cardiovascular (CV) response, is a key feature. AAIs are designed to achieve this requirement, which is reflected in their differing functional properties such as primary container selection, drug delivery mechanism (cartridge-or syringe-based), needle length, needle gauge, and adrenaline dose (150 μg, 300 μg, or 500 μg). However, the differences in functional properties across these devices may play a critical role in achieving these requirements as well as the differences in ergonomics in the handling of these devices.

THE PURPOSE OF THIS REVIEW

Considering the dynamic pharmacokinetic/pharmacodynamic (PK/PD) profiles of different AAIs marketed in Europe and their effect on adrenaline delivery, the expert panel, also serving as author for this paper have carried out a detailed analysis of the PK/PD profiles of four AAIs, namely, Anapen, Emerade, EpiPen, and Jext, to delineate the adrenaline delivery and their subsequent physiological effects on the backdrop of device characteristics, dose strength, and the skin-to-muscle distances of the participants.