A functionally-selective μ-opioid receptor agonist; functionally selective for G protein-coupled receptor signaling (EC50 = 97 nM) over β-arrestin 2 recruitment (EC50 = >10,000 nM) at the μ-opioid receptor; increases latency to withdraw in the hot plate and warm water tail-flick assay (ED50s = 6.9 and 7.7 mg/kg, respectively) without inducing respiratory depression in mice at up to 48 mg/kg