Voriconazole drastically increases exposure to oral oxycodone

Objective  We investigated the effect of voriconazole on the pharmacokinetics and pharmacodynamics of oxycodone. Methods  Twelve healthy subjects ingested either voriconazole or placebo for 4 days in a randomized, cross-over study. On day 3, they ingested 10 mg oxycodone. Timed plasma samples were collected for the measurement of oxycodone, noroxycodone, oxymorphone, noroxymorphone and voriconazole up to 48 h, and pharmacodynamic effects were recorded. Results  When voriconazole was taken at the same time as oxycodone, the mean area under the plasma concentration-time curve (AUC_0–∞) of oxycodone increased 3.6-fold (range 2.7- to 5.6-fold), peak plasma concentration 1.7-fold and elimination half-life 2.0-fold (p < 0.001) when compared to placebo. The AUC_0-∞ ratio of noroxycodone to oxycodone was decreased by 92% (p < 0.001), and that of oxymorphone increased by 108% (p < 0.01). Pharmacodynamic effects of oxycodone were modestly increased by voriconazole. Conclusions  Voriconazole inhibits the CYP3A-mediated N-demethylation of oxycodone, drastically increasing exposure to oral oxycodone. Clinically, lower doses of oxycodone may be needed during voriconazole treatment to avoid opioid-related adverse effects especially after repeated dosing.