Its a battle that you don't really care to win...or then even fight. I find it doesn't matter what opiates you use; I used heroin, morphine, methadone, tramadol, dihydrocodeine, oyxcodone, fentanyl, hydromorphone. i'm prescribed some of these for chronic pain. Its hard to want to have sex, to get a hard on and then to cum so its really an assault on all of your sex drive. I went out with a heroin addict for about a year and we rarely had sex. We would just get wasted on junk and lie around watching movies.
Now I just try and lay off the opiates for a day or two or go on Suboxone, then spend a day or two a week or fortnight getting it on with my current girlfriend(who doesn't even drink) before going back on the opiates. But as most guys know, you last like 2 seconds when in withdrawal(and even will into PAWS I found) and like I had my first wet dream when I was about 26! so having a strong dose of Codeine cough syrup (Codinex here has 15mg codeine/5ml) or maybe an Oxycontin 40mg to kinda manage to last much longer but not so much that you can't cum and are just there doing it and wanting to stop.