If by "codeine" you mean a CWE done on paracetamol/codeine tablets, then mixing with alcohol will significantly increase the damage done to the liver. So it takes less alcohol to feel sick and get a hang over. I find that alcohol hits me harder when I have had about 1g of paracetamol. Paracetamol is also more toxic when taken the day following alcohol consumption or for alcoholics in general because alcohol causes the liver to increase production of a specific enzyme system (an enzyme complex called P-450) which is a part of the biochemical detoxification process alcohol, paracetamol and other drugs undergo in the liver. The subsequent increase in the amount of P-450 increases the speed at which paracetamol it metabolised which actually greatly increases the toxicity of paracetamol. *paracetamol it self is not toxic it is its toxic metabolite (N-acetyl-p-benzoquinone imine NAPQI, or NABQI) produced in the liver by the interaction of paracetamol and P-450 enzyme complex. Yeah, so para+alcohol can make for a shitty night in the short term and bad health in the long term. EDIT: This is going to be much less of a problem for you Nozphexezora because it has been about a day since you dosed but I will include it for harm minimization purposes
I suppose the only other concerns are the increased level of sedation and the increased level of respiratory depression opiates and alcohol cause in combination, always good to keep in mind because you never can be too careful. Of course, overdose is less likely with a mug of PST than it is with a shot of smack.Again, this doesn't really apply to you because it has been around a day since you dosed the opiates but I will include it for harm minimization purposes.
Actually, I will add one more risk to opiates in-general in a social setting. When I first started using opiates to ease feelings of social anxiety and increase enjoyment at social gatherings, I think I was a little bit too naively comfortable with others knowing I was on opiates for the get together in stead of/as well as the socially acceptable alcohol, pot and stimulants. Obviously this is a generalisation and some people you know may be truly cool with it but many people, even people who believe they have an open mind about drugs are often quite deeply affected by the demonised image of the low life junky that they cannot help but look at you differently the second they get the idea that you're a recreational opiate user. This can be a real problem at gatherings with guests from work or people somehow known to you through the way you make your living. To the true believers, junkies have a disgusting, shameful, hellish existences, they are constantly in the grip of desperation and are known to steal from friends and family, many of them would walk over there dying mothers for a fix etc. The idea sounds like a ridiculous fantasy, too stupid to be real in the minds of those most important and influential to you. But the truth is that you're likely to encounter people of significance to your life who have this idea deeply woven into who they are. Even if they know you well enough and believe that you'd never lie, beg, cheat or steal for a fix, they will always think of you as the person they know who used opiates recreationally but was somehow strong enough not to turn bad. That's bad for business and all kinds of shit. I don't want to over dramatise but this actually happened to me in my early twenties and I thought it might benefit someone to read it.