This is the Weight and Healthcare newsletter! If you like what you are reading, please consider subscribing and/or sharing!
If this looks familiar, it’s because I accidentally posted it when I was working on it last week. Sorry for any confusion I caused!
I recently got a question from reader Marisol asking “I have food and bee allergies, so I carry epipens. I just came across your writing about about vaccine needles and it made me wonder about the needle on my epipen, should I be worried?”
Thanks for the question (and for those who haven’t seen it, the piece on vaccine needles is here, and the printable cards to ask for correctly sized needles are here.)
I didn’t know anything about this but I thought that it would be pretty straight forward. It was not, so shout out to my paid subscribers who made it possible for me to spend a ton of time researching this and distilling it down into something that is not novel-esque (and, of course, no shame to those who can’t or don’t want to subscribe, I’m super grateful that you are here reading this!)
First, there is a lot of controversy around epinephrine auto-injectors, including around price gouging by the pharmaceutical industry. In 2007 Mylan (now called Viatris) obtained the exclusive right to sell the epipen, with Pfizer as their sole supplier. At that time they sold the EpiPen for $57. Now the average cost for a 2-pack (preferred because of the possible need for two doses and often the only option for purchase) is $690. (In at least one case leading to a $264M settlement.) There are also issues with astroturf groups - so-called “patient advocacy groups” that are, in fact, funded by the pharmaceutical companies that sell the injectors, complicating messaging. For this piece I’m going to focus on the issues with effectiveness of epinephrine auto-injectors (EAIs) and higher-weight people, but I wanted to acknowledge these issues as well.
First, the basics. EAIs, often called “EpiPens” which is a brand name of an EAI, are used by those with severe allergies that can cause anaphylaxis which can lead to obstructed breathing and a rapid drop in blood pressure. Anaphylaxis can be fatal. EAIs are used by and for people with these allergies to start to reverse symptoms, often while waiting for emergency healthcare. Auto-injectors are prefilled with the correct amount of the drug (well, maybe…more on that later,) have clear and easy instructions printed on the side to help the patient or those around them use it correctly, and include a spring-loaded needle, making them fast and easy to use.
EAIs are recommended to be used on the muscle of the outer thigh, and here is where things can become problematic for higher-weight people.
There is some question/controversy about intramuscular vs subcutaneous injection - whether it is important for the drug to be injected into muscle tissue or if it’s fine to inject under the skin into the fat layer. (I will say that much of the controversy that I saw was generated either directly by the pharmaceutical industry and/or through research funded by the industry and/or conducted by people being paid by the industry, which doesn’t make it untrue, but is a red flag for me.) Guidance for about two decades has been that EAIs are more effective when delivered into muscle tissue than into subcutaneous/adipose tissue because intramuscular injection leads to higher peak plasma concentration than subcutaneous injection.
For this piece, I will accept the generally accepted premise that intramuscular is superior to subcutaneous injection with the caveat that new evidence could someday prove that incorrect.
Accepting that premise, in order to maximize effectiveness, the needle of the EAI must be long enough to penetrate all subcutaneous/adipose tissue and fascia and deliver the medication into the muscle, but not so long that it hits bone.
As we get into the research, I want to point out that studies on this use hypothetical models and subjects who were not experiencing symptoms since it’s not ethical to induce anaphylaxis in order to test an EAI. Also, as always, my policy is not to link to studies and articles that contain weight stigma, but to give enough information so that they can be googled.
This is not a new issue. For example, a 2009 study (Epinephrine auto-injectors: is needle length adequate for delivery of epinephrine intramuscularly? Stecher et al.) found that “The needle on epinephrine auto-injectors is not long enough to reach the muscle in a significant number of children. Increasing the needle length on the auto-injectors would increase the likelihood that more children receive epinephrine by the recommended intramuscular route.”
A 2013 study (Predictors of epinephrine autoinjector needle length inadequacy, Bhalla et al) utilized ultrasound to determine muscle depth in 120 adults. They considered the patient a potential “failure” risk if their muscle depth exceeded 15.9 mm which was the longest available epinephrine autoinjectors needle. (It should be noted that the patients are not the failure, the inadequate needle length is.) Bhalla et al. found that 31% of their sample were failure risks, with cis women at a 6.4 times greater risk than cis men (54.4% vs 5% failure rate respectively.) Unfortunately, as with most studies, this study failed to include transgender and nonbinary people. They concluded that “The current epinephrine autoinjector needle length is inadequate for intramuscular injection, especially among women.” To further complicate things, additional research has pointed out that in order for the needle to be fully in the muscle, an extra (approximately) 2mm of length over and above the muscle depth measurement is needed to make sure the needed is deep enough in the muscle that the medication is delivered there, so Bhalla et al. may well be underestimating.
That study received media coverage, including in Reuters back in 2013, so this has been a known issue for at least a decade.
A 2018 study (Bioavailability and Cardiovascular Effects of Adrenaline Administered by Anapen Autoinjector in Healthy Volunteers, DuVauchaelle et al) found that the injection needle failed to penetrate the muscle in 10 out of 12 ob*se cisgender women.
A 2019 study (Epinephrine Auto-Injector Needle Length (Does Height or BMI add Valuable Information in Adults? Drebord et al.) looked at not just body size and needle length, but also other factors that could potentially impact efficacy including whether the EAI was high pressure or low pressure (which refers to the force of the spring on the needle,) and clothing thickness (in this case, accounting for winter clothing.)
They found that when using a high-pressure EAI through naked skin with the shortest needle, 14 of 17 ob*se and 14 of 23 overw*ight cisgender women had a high risk of subcutaneous injection. Through thick clothing all 17 ob*se cis women and 20 of 23 overw*ight cis women would have a risk of subcutaneous injection. With low-pressure EAIs, through naked skin, using the shortest needle 8 of 17 ob*se and 4 of 23 overw*ight women would have a risk of subcutaneous injection, wearing thick clothing it became 10 of 17 ob*se and 7 of 23 overw*ight women.
They concluded that “Using high pressure EAIs, high BMI predicted a very high risk for subcutaneous injection in women and in some men. Even injection with low pressure EAIs had some risk of subcutaneous injection, especially when injected through thick clothing. Height had no predictive value.”
As always, a reminder that BMI is a deeply flawed concept.
So adequate needle length and low-pressure injection seem to be important for higher-weight people. But there is still the matter of dosage: Do higher-weight people need higher doses of epinephrine?
A 2022 study (International recommendations on epinephrine auto-injector doses often differ from standard weight-based guidance: a review and clinical proposals by Dreborg et al) took on this question.
They noted that “The majority of national and regional professional societies and authorities recommend epinephrine delivered by auto-injectors at doses far lower than the generally accepted therapeutic dose of 0.01 mg/kg body weight.” They also point out that while this is the generally accepted dose, it has not been tested scientifically, in large part due to the ethical issues mentioned above.
They point out that a combination of inadequate needle length (leading to “slower systemic distribution than intramuscular (IM) injection”) and lower-than-recommended dose can explain the “relative increase in anaphylaxis fatalities in women with higher body mass indices in the community; a well-documented phenomenon.” (They cite four studies from 2000 to 2021 to back up this statement.)
They do note that “The influence of epinephrine on patients with easily triggered cardiac complications such as arrhythmias and a tendency towards myocardial infarction must be considered whenever injecting this medication.”
In terms of recommendations they say “In children, a higher dose than that generally recommended appears to be well tolerated. Therefore, it is likely reasonable to at least increase the dose to 0.15 mg in children weighing 10–25 kg and to 0.3 mg in children weighing 25–40 kg. Likewise, the 0.5 mg dosing should be tolerated by adolescents and young adults weighing more than 40 kg. Healthy adults weighing more than 50 kg would likely benefit from the 0.5 mg dose.”
They conclude “We suggest prescribing more appropriate doses of epinephrine auto-injectors based on weight-based recommendations. There may be some exceptions, such as for patients with heart disease. We hypothesize that these recommendations will lead to improved outcomes of anaphylaxis.”
It should be noted that the authors of this study take money from pharmaceutical companies that make these pens.
One other thing I want to point out is that their recommendations stop at “more than 50kg” (about 110 pounds.) This suggests to me that they aren’t considering, let alone including, higher-weight people in their thinking here. If the medication is typically dosed by weight, then it’s ludicrous to assume without testing that a dose that is adequate for someone who weighs 110lbs would be adequate for someone who weighs several times more. This is another way in which weight stigma in medical research means that higher-weight people are underserved. They acknowledge that since at least 2000 there have been higher rates of anaphylaxis fatalities in higher-weight cis women, then tap out at 110lbs in their recommendations. Research needs to do better than this.
What Can Be Done
This isn’t just a problem for higher-weight people, it could also impact people who are traditionally thin but happen to have a thicker layer of fat on their thighs, or even someone who typically wears thick clothes (especially if they aren’t easy to remove.) As always, I’m not offering medical advice here and you should check with a qualified (preferably weight-neutral) practitioner.
One option is to measure the patient's skin-to-muscle depth by ultrasound when the EAIs are prescribed, and then find an EAI with the correct length needle.
If you are a patient you can ask for this and if you are a practitioner you can initiate it.
There is a table here with brands of EAIs including needle lengths (as of 2019.)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7160976/table/Tab1/?report=objectonly
Note again that they suggest subtracting 2mm from the length of needle as advertised to make sure that the medication is delivered intramuscularly.
Of course, the fact that an EAI that works for someone exists doesn’t mean that it is accessible/affordable for them.
In my research there was consensus that a too-short needle is still better than nothing.
Using the needle on bare skin can also help.
Another tip I came across was to push down as hard as you can when giving the injection.
On a much larger scale, we need much more research about this – this is a life and death medication and the fact that fat people weren’t included in research and manufacturing from the beginning is unconscionable, but the fact that the latest research still says that we need more research for a problem that has been identified for over twenty years is simply unacceptable and is an example of one of the many ways that fat people’s healthcare is compromised by weight stigma.
Higher-weight people deserve far more from our healthcare.
Did you find this post helpful? You can subscribe for free to get future posts delivered direct to your inbox, or choose a paid subscription to support the newsletter and get special benefits! Click the Subscribe button below for details:
Like the piece? Share the piece!
More research and resources:
https://haeshealthsheets.com/resources/
*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.
As an EpiPen carrier, a nurse, and a fat person, this post really got to me. We're taught in school that certain sites on the body--including the lateral (outside) thigh (vastus lateralis muscle) has only an inch of subcutaneous tissue overlying it, in most body types, even fat ones. The ultrasound findings in the study you cite obviously contradict that. This is yet another example of nursing education based on thin bodies/baseless assertions of effectiveness. And a complete lack of accountability in the drug approval process. Class action lawsuit, anyone?
So curious to know if similar issues exist in other auto-injector medications such as HRT, humira, and migraine medications like emgality. Just another way that multiply marginalized people such as fat trans folks and/or fat chronically ill folks are continually underserved.