Your certain those are 20s??? I think you got 10s man the 20s shouldn't be round which was my first clue and somebody else posted saying they double checked a pill finder online.
Go on google and be sure what you got if your not getting these from a pharmacy.
I've always found the same thing when it came to roxicodone or oxycontin they were always the ones that packed the most punch and were the only ones really worth IVing. I wouldnt IV these pills you have anymore not worth it. The generic brands generally have different fillers which make it great for releasing quickly in the stomach but not to go in your veins and although the active ingredient is the same I do believe strongly that the generic brands such as supedol don't pack as much of a punch and they are chalkier when you crush them compared to roxicodone/oxycontin. I find these pills you have work best when eaten because of the way they are made to dissolve quickly in the stomach but still I've always found the same thing they just don't seem to get me very high they just seem to to take care of my pain/withdrawal symptoms.
The roxicodone seems to be pretty close to heroin because they smoke like heroin, don't have many fillers, are easy to IV and pack a punch(strong high) whereas the chalkier generic pills are more like good old percocets. No strong overwheming heroin like high but great for pain/withdrawal though.