my dr recently switched my pain medication to morphine so4 tab,sa does anyone know what the so4 stands for also what the SA stands for.. i have been on vicodin for years but it has stopped working so they switched to this but i can not find what the so4 and sa stand for or if its imediate release or slow release.. i tried the pill identifer and it showed morphine sulfate sl... but the bottle does not say sulfate or sl but it did look like the same pill it is round and orange and small it has an m in a square and 60 on the other side.. does anyone know the difference between what i have an the morphine sulfate thanks