Mixing opiates and alcohol is bad. Very bad. I seem to remember hearing that drinking a shot ~10-20 mins before ingesting codeine helps release an enzyme which breaks down more codeine quicker? That seems to spring to mind from when I researched codeine a very very long time ago but I don't know how reliable that is, whether it's true or not and if there's any scientific evidence for it. Either way you shouldn't mix alcohol with codeine as they're both depressants and make it easier to OD (note I'm not saying it's easy to OD from doing 1 shot of vodka and a low dose of codeine since codeine is a relatively weak opiod but please do some research).