RWJ-394674 is a drug that is used in scientific research. It is a potent, orally active analgesic drug that produces little respiratory depression. RWJ-394674 itself is a potent and selective agonist for ô-opioid receptors, with a K<sub>i</sub> of 0.24 nM at ô and 72 nM at ü. However once inside the body, RWJ-394674 is dealkylated to its monodesethyl metabolite RWJ-413216, which is a potent agonist at the ü-opioid receptor and has less affinity for ô (K<sub>i</sub> of 0.26 nM at ü, 46.7 nM at ô). The effect of RWJ-394674 when administered in vivo thus produces potent agonist effects at both ü and ô receptors through the combined actions of the parent drug and its active metabolite, with the ô-agonist effects counteracting the respiratory depression from the ü-opioid effects, and the only prominent side-effect being sedation.