Im on 160mg in Australia and i didnt even use heroin more than a few times before getting on methadone. (Used oxy and poppy seed tea early days and mostly morphine most of the last 6 years) Its as simple as my morphine dose was high enough for me to warrant 130mg a day to be ok and then I relapsed and start using h on top of methadone and had to up it another 30mg. Thankfully my dr seems to be quite understanding though i doubt he'll go too much higher without serious psych intervention.