Ive always found one of the side effects of codeine to be nausea, so im not sure. Like emily said could you not get benzos?
I know docs are very tight at prescribing them, with doses that wouldnt calm a mouse down, like 2mg od diazapam. But im sure they would give you something? And if your tolerance is zero, they might just help.
For me codeine would be the wrong drug as it causes euphoria. Id probably change my mind after taking it and walk the streets preaching about world peace instead of ctb.