1) Synthetic opioid 
Ciprefadol is an opioid analgesic that is an isoquinoline derivative most closely related to cyclazocine and picenadol, with a number of other related compounds known. Ciprefadol is a mixed agonist–antagonist at μ-opioid receptors and can partly block the effects of morphine at low doses, though at higher doses it acts more like a full agonist....