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
| Name | Oxycodone |
| Class | Opioid |
| Chemistry | Semisynthetic phenanthrene |
| 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.