I wouldn't recommend mixing heroin with any RX, unless it's something you are already tolerant to, educated on, and/or prescribed. If you have a daily habit of using either one, I can understand the mixing a bit more, though. (Simply due to the fact that at the brink of withdrawal from one opiate, you may score another to prevent getting sick)
Personally, I'd say pick your poison. If you and your buddies are more into heroin, stick to heroin. If you like pills, I'd say go with Oxycontins. You can always break an Oxycontin up into quarters, or if you're tolerant...you can go for a bit more (depending on the milligrams/tolerance involved).
If you're shooting dope you shouldn't need to snort anything else, though! Besides, you're then left with a higher possibility of ODing. If you're on a substantial amount of painkillers PRIOR to shooting dope, you must always take that into account before you IV anything.
Know what you're putting into your body. Think about how much heroin you're thinking of obtaining. Will you seriously need more opiates, or would you end up getting a good nod off of the H alone? Not to be rude, but it sounds as though you're a bit too eager (which is understandable, haha) and not 100 percent certain as to what you're doing. Either that or you're careless. Personally, heroin plus painkillers all at once is a waste of money to me. Whatever the hell you end up doing, be safe! :D
