Suboxone. To clarify, suboxone is an opiate as is methadone (synthetic opioid), however, unlike other painkillers such as oxy, hydro, morphine, heroin (diacetyl morphine) and others, suboxone is what is referred to as a partial agonist. There are 2 major receptors which receive opiates: the mU and the Kappa receptor. The mU receptor is responsible for that feeling of euphoria while the Kapaa receptor once blocked is responsible for that anti-depressive "everything is fantastic" feeling. While typical opiates and methadone fulfill both of these receptors and stimulate them (the clinical word is antagonize), suboxone fills both but only antagonizes the Kappa receptor so you get the feeling that everything is going to be awesome without the euphoria and drowsiness seen in other opiates. In fact, due to this phenomena, it is my understanding that it is being clinically trialed as an anti depressant in individuals where conventional SSRI drugs have had little or no effect.