Propoxyphene.

T he d-isomer of synthetic diphenyl propionate derivative propoxyphene, with narcotic analgesic effect. T his agent mimics the effects of the endogenous opiate dextropropoxyphene, by binding to mu receptors located throughout the central nervous system. T he binding results in GT P to GDP exchanges on the mu-G-protein complex, by which effector adenylate cyclase is inactivated thereby decreasing intracellular cAMP. T his, in turn, inhibits the release of various nociceptive neurotransmitters, such as substance P, gamma-aminobutyric acid (GABA), dopamine, acetylcholine, noradrenaline, vasopressin, and somatostatin. In addition, dextropropoxyphene closes N-type voltagegated calcium channels and opens calcium-dependent inwardly rectifying potassium channels. T his results in hyperpolarization, thereby reducing neuronal excitability, which further decreases the perception of pain. Qeios · Definition, February 7, 2020