i can't speak for the RX robitussin, but i know when i take Tussionex which has hydrocodone in it it knocks me out, and i have somewhat of a tolerance to pain medication as well. I think hydro is about 4 or 5 times stronger than hydrocodone though so with your tolerance i don't think it will knock you out. I've taken other cough meds with codiene in them and they didn't seem as strong as Tussionex. hope this helped.