Question 12

Describe the pharmacology of oxycodone.

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College Answer

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.