Receptor Affinity & Selectivity of Common Opioid Agonists

Buprenorphine: mu partial agonist, kappa antagonist, ORL1-partial agonist

Morphine: mu agonist, delta & kappa agonist (in high doses) . 38/1 mu/kappa selectivity

Oxycodone: predominant mu agonist, delta & kappa agonist (very low affinity) . 135/1 mu/kappa selectivity

Hydrocodone: mu agonist, delta & kappa agonist (in high doses) . 68/1 mu/kappa selectivity

Hydromorphone: mu agonist, delta & kappa agonist (in high doses) . 26/1 mu/kappa selectivity

Oxymorphone: mu agonist, delta & kappa agonist (in high doses) . 82/1 mu/kappa selectivity

Levorphanol: mu agonist, kappa agonist, delta agonist, NMDA antagonist, 5HT & NE reuptake inhibitor . no selectivity

Methadone: predominant mu agonist, NMDA antagonist, nACh antagonist, delta & kappa agonist (very low affinity) . 493/1 mu/kappa selectivity

Fentanyl: predominant mu agonist, delta & kappa agonist (very low affinity) . 121/1 mu/kappa selectivity

Etorphine: mu agonist, kappa agonist, delta agonist . no selectivity

Codeine: mu agonist, delta & kappa agonist (in high doses) . 35/1 mu/kappa selectivity

Tramadol: selective mu agonist (very low affinity), 5HT & NE reuptake inhibitor . high selectivity