The formulation of the brand-name Norco tablets includes two inactive ingredients that are not in the generic version (also made by Watson), otherwise they are identical. However, I've noticed a difference -- the brand name Norco tablets that I got from a local pharmacy on two different occasions made me nauseous, to the point that I could not take them and had to throw them away. I have no way of knowing exactly why I had this reaction, but there were some other people who said they had a similar experience with brand Norco. Needless to say, I never request the brand name tablets.

The difference in the amount of tylenol in the different strengths has no effect on the efficacy of the narcotic -- in other words, APAP doesn't "potentiate" hydro, the only difference would be the added minor amount of pain relief that the higher dosage of tylenol would give you. It certainly is a good idea to take less apap, especially over the long term.