R-4066

Overview
R-4066 is a drug which is an analogue of the opioid analgesic methadone, where the metabolically labile dimethylamino group has been replaced by a piperidinospiro group. It is around 212x more potent than methadone as an analgesic in animal tests, with an effective oral dosage of 0.07mg/kg, but is slightly shorter acting, with a duration of action of around 3 hours.

R-4066 has never been used in humans, but would be expected to produce effects similar to those of other potent opioid agonists, including strong analgesia, sedation, euphoria, constipation, itching and respiratory depression which could be harmful or fatal.