Describe the pharmacology of oxycodone.
Few candidates covered the pharmacokinetic aspect of the question sufficiently.
No marks were awarded for generic comments such as hepatic metabolism and renal excretion
|Routes of administration||Oral, IV|
|Absorption||Well absorbed orally, 80% bioavailability|
|Solubility||pKa 8.5, quite hydrophilic|
|Distribution||VOD = 2.6L/kg; 38–45% protein-bound|
|Target receptor||mu-opiate receptor (pre-synaptic G-protein coupled receptor)|
|Metabolism||Hepatic metabolism; notable metabolites include noroxycodone and oxymorphone, both active metabolites|
|Elimination||Minimal unchanged drug cleared renally, but most of the metabolites rely on renal excretion|
|Time course of action||Half-life 3-5 hours|
|Mechanism of action||Hyperpolarisation of cell membrane by increasing potassium conductance; reduced production of cAMP and closure of voltage-gated calcium channels|
|Clinical effects||Analgesia, respiratory depression, constipation, miosis, urinary retention.|
|Single best reference for further information||Crow et al (2021)|
Zöllner, C., and C. Stein. "Opioids." Handbook of Experimental Pharmacology (2006): 31-63.
Crow, Jessica R., Stephanie L. Davis, and Andrew S. Jarrell. "Pharmacology and Pharmacokinetics of Opioids in the ICU." Opioid Use in Critical Care. Springer, Cham, 2021. 31-64.
Cata, Juan P., and Shreyas P. Bhavsar. "Pharmacology of opioids." Basic Sciences in Anesthesia. Springer, Cham, 2018. 123-137.