Oxymorphone, pharmacokinetics

Pharmacokinetic properties Oxycodone (Kaiko et al., 1996) is well absorbed from the gastrointestinal tract. It is metabolized to nor-oxycodone and to a lesser extent to the active metabolite oxymorphone (Poyhia et al., 1993). Metabolites and unchanged parent drug are excreted in the urine. 

Pharmacokinetic properties Oxymorphone is excreted into the urine as the unmetabolized drug and to a greater extent as the O-glucuronide (Cone et al., 1983). 

A number of drugs of abuse are known substrates (e.g., codeine, hydrocodone, p-methoxyamphetamine, amphetamine) or inhibitors (e g., (-)-cocaine, pentazocine) of CYP2D6. For some of these drugs, the pharmacokinetic differences due to the polymorphism will be so profound that they are likely to exceed pharmacodynamic sources of variation in response. For other drugs (e.g., hydrocodone to hydromorphone, codeine to morphine, oxycodone to oxymorphone), CYP2D6 may not contribute importantly to the overall clearance of the drug, but may catalyze the formation of highly active metabolites. 

For morphine, hydromorphone, and oxymorphone, rectal administration is an alternate route for patients unable to take oral medications, but equianalgesic doses may differ from oral and parenteral doses because of pharmacokinetic differences. 

The use of oxymorphone ER has a series of potential advantages stemming from issues relating to clinical practicality, ease of use, as well as favorable pharmacodynamic and pharmacokinetic attributes. Oxymorphone ER has high analgesic uniformity, with minimal fluctuations in plasma concentration when dosed every 12 hours during steady state [2]. Such limited variation in the oxymorphone plasma concentration... 

Adams MP, Ahdieh H. Pharmacokinetics and dose-proportionality of oxymorphone extended... 

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