Table 2. Comparison of the Affinity [Ki (µM)] of Tapentadol and Morphine at Various Opioid Receptor Subtypes in Rat Brain Membranes or Human Recombinant Receptors [6,7].

MOR: mu-opiate receptor, KOR: kappa-opiate receptor, DOR: delta-opiate receptor, NOP (ORL1): nociception receptor (opioid receptor-like receptor).