^alcohol effects the metabolism of codeine in a very specific way. inhibits and/or delays. which may or may not be a good thing, because some of the codeine metabolizes into morphine. but maybe it could make the high last longer. i've read a bunch of journal articles trying to figure out when would be the best point in time (e.g. right before, an hour into, etc.) to drink in order to stretch out the positive feeling of codeine--if it is even possible. but i couldn't understand their charts. privately run experiments confirmed my hypothesis that alcohol makes codeine feel better anytime. but i don't know about making it last longer.
of course in the name of HR, gotta mention that combining two CNS depressants like alcohol and codeine is dangerous because it increases the chance of fatal respiratory depression. ADD told me so...