If this is your first time doing Codeine, do not mix it with Promethazine, especially if it is on a dose to dose basis equivalent to the Codeine.
If you have done Codeine before, taking 25kmg of promethazine before taking your dose would synergize well to the high and give you a nod. Anything above 25mg, before or after you dose, will overpower the high and ruin it. Prometh is not to be messed with if you don't have a tolerance to it.
And 8 oz is going to have like 400+mg of codeine not 120 man do not drink the whole bottle if you have no tolerance good god.