My understanding is that the typical adult prescription is for two epi-pens with the instructions basically being, use the first one and if there is not a rapid reduction in the symptoms, give the second. Call for help immediately after the first pen.

My wife's doctor also recommended fast melt benadryl (diphenhydramine) and Zantac. The first is an anti-histimine and the second is a histamine blocker. Not being a Dr. or biochemist all I can tell you is they work differently in the body to help reduce the reaction. If my wife detects the early symptoms we can avoid using the epi-pens by rapidly giving her a full adult dose of the Benadryl and at least one Zantac 75. Her symptoms usually stabilize within 30 minutes of taking these over the counter medicines but I usually end up watching her for several hours after while she sleeps off the benadryl.

To abuse a great line - "Darnit! I'm an Engineer, not a doctor".

Seek professional advice and guidance if this is a concern for you or yours.

-Eric