Oxycodone is an opioid used in the management of moderate to severe pain. There is also an extended release formulation indicated for chronic moderate to severe pain requiring continuous opioid analgesics for an extended period. Oxycodone acts directly on a number of tissues not related to its analgesic effect. These tissues include the respiratory centre in the brain stem, the cough centre in the medulla, muscles of the pupils, gastrointestinal tract, cardiovascular system, endocrine system, and immune system. Oxycodone's effect on the respiratory centre is dose dependant respiratory depression. The action on the cough centre is suppression of the cough reflex.\ Pupils become miopic or decrease in size, peristalsis of the gastrointestinal tract slows, and muscle tone in the colon may increase causing constipation. In the cardiovascular system histamine may be released leading to pruritis, red eyes, flushing, sweating, and decreased blood pressure. Endocrine effects may include increased prolactin, decreased cortisol, and decreased testosterone. It is not yet known if the effects of opioids on the immune system are clinically significant. Oxycodone is an opioid used in the management of moderate to severe pain. There is also an extended release formulation indicated for chronic moderate to severe pain requiring continuous opioid analgesics for an extended period. Oxycodone acts directly on a number of tissues not related to its analgesic effect. These tissues include the respiratory centre in the brain stem, the cough centre in the medulla, muscles of the pupils, gastrointestinal tract, cardiovascular system, endocrine system, and immune system. Oxycodone's effect on the respiratory centre is dose dependant respiratory depression. The action on the cough centre is suppression of the cough reflex.\ Pupils become miopic or decrease in size, peristalsis of the gastrointestinal tract slows, and muscle tone in the colon may increase causing constipation. In the cardiovascular system histamine may be released leading to pruritis, red eyes, flushing, sweating, and decreased blood pressure. Endocrine effects may include increased prolactin, decreased cortisol, and decreased testosterone. It is not yet known if the effects of opioids on the immune system are clinically significant. Oxycodone binds to mu opioid receptors, stimulating the exchange of GTP for GDP on the G-protein complex. As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as GABA is inhibited. Opioids close N-type voltage-operated calcium channels and open calcium-dependent inwardly rectifying potassium channels. This results in hyperpolarization and reduced neuronal excitability. Oxycodone acts at A delta and C pain fibres in the dorsal horn of the spinal cord. By decreasing neurotransmitter action there is less pain transmittance into the spinal cord. This leads to less pain perception. Oxycodone may also bind to delta and kappa opioid receptors.

Oxycodone Opioid Agonist Pathway References