For departures from the US, the TSA web page specifically mentions that Epi-pens _are_ permitted in your carry on luggage. ALL prescription and over the counter medication is allowed.
Also for US departures, the TSA does _not_ need to see any prescription label, does not need to have pills and so on in any original pharmacy bottle. While it is always a good idea to carry items such as an Epi-pen in an original box, it is not necessary in the US.
If you depart from another country, the rules on having a prescription label are different.
I travel with two types of insulin pens, needles for those, testing meters, alcohol swabs and a couple of prescription pills. I have never been asked about any of it. No TSA person has wanted to take a close look at any of it. I keep photocopies of the prescription labels in my travel kit, but nothing is in an original container/box, and I have never needed to show those photocopies to anyone.
The TSA inspectors see many, many people every day with medical items such as yours. It will not be unusual.