TRIMU-5 is a selective agonist of the ü<sub>2</sub>-opioid receptor and antagonist of the ü<sub>1</sub>-opioid receptor. It produces analgesia in animals that differs from that of conventional ü-opioid receptor agonists but that can still be blocked by ü-opioid receptor antagonists. TRIMU-5 can also block the analgesic effects of ü-opioid receptor agonists like morphine. In addition to analgesia, TRIMU-5 inhibits gastrointestinal transit, a known effect of ü<sub>2</sub>-opioid receptor activation.