Pharmacokinetics of Intramuscular Adrenaline in Food--Allergic Teenagers: Does Dose Matter?

Food allergy affects up to 2% of adults and 8% of children in the United Kingdom (UK), and is a major public health issue. It is the commonest cause of life-threatening allergic reactions (anaphylaxis), which can be fatal. Adrenaline (epinephrine) auto-injector (AAI) devices are the first-line treatment for anaphylaxis, yet in a UK survey, over 80% of 245 teenagers experiencing anaphylaxis did not use their AAI. Delays in, or lack of adrenaline (epinephrine) administration during anaphylaxis are risk factors for fatal anaphylaxis.

In 2010, a coroner's investigation into the death of a food-allergic teenager in the UK raised several questions around AAI safety and efficacy, since the teenager died despite administering her auto-injector device. This prompted a review by the Medicines and Healthcare products Regulatory Agency (MHRA) in 2014 into the clinical and quality considerations of AAIs. Two recommendations which came from the review was that companies 'should be encouraged to develop a 0.5mg [dose] AAI.' In the UK currently only Emerade, one of the three companies selling AAIs, manufactures a 0.5mg (500mcg) version. Emerade also has a longer needle length (23mm) compared to other AAIs (typically 15mm).

The investigators plan to formally assess the pharmacokinetics (PK) and pharmacodynamics (PD) of self-injection with intramuscular adrenaline (epinephrine) in teenagers at risk of anaphylaxis due to food allergy, and have been prescribed AAI.

1. The investigators will compare self-injection with 300mcg vs 500mcg in teenagers of body weight >40kg. In a 40kg person, an adrenaline dose of 300mcg results in an effective UNDER-dosing of 30% by body weight.
2. The investigators will also assess the impact of needle length on injection, by comparing two different devices, both of which deliver 300mcg, but one via a 15mm needle and the other with a 23mm needle.