PZM21 is a potent Gi activator with exceptional selectivity for μOR and minimal β-arrestin-2 recruitment. PZM21 is an experimental opioid analgesic drug that is being researched for the treatment of pain. It is a functionally selective μ-opioid receptor agonist which produces μ-opioid receptor mediated G protein signaling, with potency and efficacy similar to morphine, but with less β-arrestin 2 recruitment. In tests on mice, PZM21 was slightly less potent than morphine or TRV130 as an analgesic, but also had significantly reduced adverse effects, with less constipation than morphine, and very little respiratory depression, even at high doses.
