A number of important studies have been conducted recently which relates to the inadequacy of the Epipen’s needle length when applied by certain types of patients who are suffering from anaphylaxis
Put simply the adrenaline from any adrenaline injector must be injected into a muscle. The problem is that the needle has to first pass through a layer of fat and for some people with a thick layer of fat, the needle simply does not penetrate sufficiently to reach the muscle. For over a quarter of women the Epipen needle length is not enough.
At the moment most auto-injectors have a needle the same needle length – around 15.2 mm – and in a recent study it was shown that of 100 patients, 19 patients were shown to have a fat layer greater than 15.2 mm and without exception all those 19 patients were women. The study goes on to show that some 28% of women are at serious risk of their adrenaline not being appropriately administered because of the higher than average levels of fat on their thighs.
In the US the recommended needle lengths for new borns are 16 mm, children between 1 and 12 years old 25 mm, and adults from 25 mm to 31 mm. In the UK the Resuscitation Guidelines recommend a 25 mm needle for all ages.
The Epipen and Jext autoinjectors do not meet the UK Resuscitation Council Guidelines with their longest needles being only 15.0 and 15.4 mm respectively. Insofar as needle length is concerned there is only one adrenaline auto-injector that appears to meet Resuscitation Guidelines – the Emerade.
Patients, and women in particular, should therefore make their prescribing doctor aware of these issues and insist that needle length be taken into consideration when prescribing their auto-injector.