Your freind doesn't know what s/he is talking about.
Vicodin is a brand name for hyrdocodone and a anti-inflamatory which is I think always tylenol, also known on the bottle of vicodin as APAP.
So if you get a prescription of vicodin it would look something like this:
5/500 APAP. The 5 indicating how much hyrdocodone (the good stuff) and 500 APAP which is tylenol (the bad stuff).
APAP is really hard on the liver so don't take over 2500 - 3000 grams per day.
There are also lorcet, lortab, norco, etc., which are all the same thing, just different quantities of hydro and APAP.