I'm pretty sure it is the antihistamine used in Benadryll. I am also pretty sure it can be habit forming, meaning that you may have trouble sleeping if you take it for long periods of time before...
Vicodin is made as a mixture of hydrocodone and paracetamol. Paracetamol, which is also called acetaminophen, acts as an analgesic/antipyretic. Hydrocodone is a semi-synthetic opioid.
Vicodin...
I would think it being an antibiotic that it is a relative to penicillin For people who can't take penicillin Just a educated guess. Maybe someone can say more but if your looking to get a buzz...