Epi Pen Wilderness Protocols

Recently a colleague asked me about the timing for the administration of an epi-pen in a wilderness setting. They had originally been taught to delay the administration of epinephrine until the patient could only say one or two words and explaining “we were taught to hold off the epi-pen use. We only have so much epi and hopefully the anti-histamines would kick and would not need the epi”. In my colleagues latest recertification the same organization is now teaching administer the epi-pen as soon as signs and symptoms of anaphylaxis shock manifest. They wanted to know what I was teaching in my classes.

My reply:  

As for your question I was taught and teach to administer the epi-pen as soon as S/S of anaphylaxis shock manifest along with a dose on antihistamines based on the patients LOC/LOR . (note in the event that someone is unconscious you can place it under their tongue). The science behind this is as follows:

1) The antihistamines do nothing for the first release of histamines by the body but will help with a potential second release. A note hear is that Auerbach (Wilderness Medicine edition 5 page 2120) suggests there may be some benefit using antihistamines as a prophylactic in individuals that are predisposed to anaphylaxis shock. 

2) The onset of S/S is commonly 5 to 30 minutes after contact with the allergen and can occur up to 2  hours later. 

3) The absorption rate of Benadryl (diphenhydramine) is 1.7 hours plus or minus 1.0 Hours (see  http://www.jiaci.org/issues/vol16s1/2.pdf) and 

4) The absorption rate of epinephrine is 117.7 minutes plus or minus 30.8 minutes (see http://www.ncbi.nlm.nih.gov/pubmed/10870098 ) note this primarily deals with the rates of absorption through subcutaneous, intramuscular and intravenously

I have read some articles on the administration of the second dose not being necessary if you will be at the hospital in less than 2 hours (note this may be supported based on the rates of absorption listed above) and believe  this may be the American Safety & Health Institutes position also.