Oxycodone is a Schedule II semi-synthetic opiate derived from thebaine and is part of the phenanthrenes group that is based off the morphine structure1. Additionally, this drug is a µ receptor agonist2. It is prescribed under the following trade names: Oxycontin, Oxycet, Roxicodone, Endocet, Endodan, Percocet, Percodan, and Roxicet. Oxycodone is prescribed as a narcotic analgesic for moderate to moderately severe pain.
Oxycodone is administered orally via a solution, tablet or capsule with typical doses of 5-100 mg/5 mL or 2.5-30 mg, respectively. Additionally, an extended release formulation with a dose of 10-80 mg is available. Frequently, drugs such as acetaminophen, aspirin, or ibuprofen are present in the medication4.
Following a 10 mg oral dose of oxycodone, peak serum concentrations occurred around 0.8-2.5 hours with a half-life of 3-6 hours4. Oxycodone has a high bioavailability of up to 60%2.
Oxycodone is metabolized extensively in the liver by demethylation at the O and the N positions in order to form oxymorphone (OM) and noroxycodone (NOC), respectively2,4. Oxycodone is metabolized through the CYP2D6 enzyme to produce the pharmacologically active metabolite OM. Due to a genetic polymorphism of CYP2D6, this metabolic pathway may have reduced metabolism, which may adversely affects the therapeutic efficacy5. Pharmacologically inactive NOC is metabolized by CYP3A4 and is unaffected by the CYP2D6 polymorphism.
The majority of the parent drug and metabolites are excreted over a phase of 36 hours, with approximately 72% being present in the 48 hour urine4,6.
Oxycodone demonstrates poor cross-reactivity with the opiate assay; therefore, the highly specific oxycodone screening Enzyme Immunoassay (EIA) methodology is utilized for the detection of oxycodone with a cutoff concentration of 300 ng/mL . Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) is used to confirm and quantify oxycodone, with a cutoff concentration at 20 ng/mL. Subsequent to analyses, the urine concentrations of oxycodone and its two primary metabolites are reported.
For patients regularly prescribed oxycodone, the parent drug along with the metabolites should be detected in the urine. In a study conducted by Heltsely, et al., of 5046 specimens analyzed for oxycodone, 65.3% contained both oxycodone and metabolites, 14.9% contained only metabolites of oxycodone and 4.0% contained only parent drug7. If only oxycodone is present in high concentrations, the possibility of patient tampering should be considered.
The interpretation of patients prescribed oxycodone should be conducted with caution since OM is also prescribed and/or abused. NOC is metabolized directly from oxycodone and has a longer detection time; therefore it may assist with interpretation8. Additionally, oxycodone preparation may contain hydrocodone as an impurity up to 0.12% and oxycodone is a known impurity in oxymorphone preparations up to 0.4%9.