the me analog of fentanyl mef was first introduced by paul janssen j med chem which has been recently revisited by slavic researchers j serb chem qsar reveals that the oh was first incorporated into mef because this pharmacophore had previously been shown to raise the potency of closely related piperidine based narcotics j med chem such as phenoperidine for example afaik ohmefentanyl was first reported by chinese chemists in scienta sinica vol xxiv no pp may since that time both chinese and also american scientists submitted the first elaborate evaluations on omf isomer variations in in the jmc j med chem j med chem