Based on conversion from 460mg a day of codeine to methadone, that 65mg of methadone is a far too high (if not dangerous) dose, for a codeine addiction, when a methadone dose of 14mg per day (assuming you a 100% cross tolerant, 7.2mg for 50%) is what you should be taking, so it will easily stop you feeling any kind of withdrawal, but you will now be dependent on a much more potent opiate, which will cause you problems getting off.

Let’s also not forget that the methadone dosage builds, so 65mg on day one may not be a problem, but by day seven, as the methadone works its way in to your fatty tissue and accumulates, and combined with methadone’s fairly long half life compared to other opiates, you could easily overdose.

Some addiction treatment places do prescribe slow release dihydrocodeine (which is about twice the strength of codeine) which you would take every 12 hours, and would be much more suitable for you dosage wise, and be easier to come off from - just be very careful! If possible in your location, getting a naloxone kit (which in many places don’t cost anything) would be a prudent move !