drugs, PSA
BTW, @aschmitz added some wonderful advice onto this that I highly recommend you read. I'd just like to add two more things myself:
1) Not only is injectable naloxone cheaper, but intramuscular injection is generally more effective, so if you're comfortable with IM injections, that's definitely the preferred route.
2) If you ever administer naloxone, you need to get that person into a hospital or otherwise transfer them to emergency care (say, EMTs). It's not a substitute for that.