I know this isn't normally the kind of thing we post in BDD, but I found the results of this study so amazing I figured it was worth sharing. I posted it as a reply in another thread, but I really feel this information shouldn't be overlooked. They are talking about 1.5 fold increases in peak plasma concentration and 1.2 fold increase in half life (with a very low p-value for those who like their statistics significant). The test subjects ingested 200ml of grapefruit juice 3 times per day for 4 days before the oxycodone was administered. I think this is evidence enough to state that drinking grapefruit juice on a daily basis can have a very significant impact on oxycodone metabolism.
Grapefruit juice enhances the exposure to oral oxycodone
Nieminen T.H., Hagelberg N.M., Saari T.I., Neuvonen M., Neuvonen P.J., Laine K. and Olkkola K.T.
Basic and Clinical Pharmacology and Toxicology 2010 107:4 (782-788)
Grapefruit juice alters the concentrations of many CYP3A substrates. The objective of this study was to examine the effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of oral oxycodone in a randomized cross-over study with two phases at an interval of 4 weeks. Twelve healthy volunteers ingested 200 ml of grapefruit juice or water t.i.d. for 5 days. An oral dose of oxycodone hydrochloride 10 mg was administered on day 4. Oxycodone, noroxycodone, oxymorphone and noroxymorphone concentrations were analysed from the plasma samples for 48 hr and behavioural and analgesic effects were recorded for 12 hr. Grapefruit juice increased the mean area under the oxycodone concentration-time curve (AUC0-∞) by 1.7-fold (p < 0.001), the peak plasma concentration by 1.5-fold (p < 0.001) and the half-life of oxycodone by 1.2-fold (p < 0.001) as compared to the water. The metabolite-to-parent AUC0-∞ ratios (AUCmAUC p) of noroxycodone and noroxymorphone decreased by 44% (p < 0.001) and 45% (p < 0.001), respectively. Oxymorphone AUC0-∞ increased by 1.6-fold (p < 0.01) after grapefruit juice, but the AUC mAUCp remained unchanged. Pharmacodynamic changes were modest and only self-reported performance significantly impaired after grapefruit juice. Analgesic effects were not influenced. Grapefruit juice inhibited the CYP3A4-mediated first-pass metabolism of oxycodone, decreased the formation of noroxycodone and noroxymorphone and increased that of oxymorphone. We conclude that dietary consumption of grapefruit products may increase the concentrations and effects of oxycodone in clinical use.