The single-dose and steady-state pharmacokinetics and pharmacodynamics of oxycodone have been determined in patients with moderate to severe cancer pain. The mean +/- SD elimination half-life after single-dose administration of intravenous (4.6 mg to 9.1 mg) and oral (9.1 mg) oxycodone was 3.01 +/- 1.37 hours and 3.51 +/- 1.43 hours, respectively. After intravenous administration, the mean +/- SD volume of distribution was 211.9 +/- 186.6 L, and the mean +/- SD total plasma clearance was 48.6 +/- 26.5 L/hr. The mean absolute oral bioavailability of oxycodone was 87%, and the mean +/- SD volume of distribution after oral administration was 249.1 +/- 204.3 L. When administered orally as 10 mg oxycodone hydrochloride every 4 hours, there was no accumulation of oxycodone at steady state and the mean +/- SD steady-state concentration was 34.6 +/- 10.3 micrograms/L. Intravenous oxycodone produced a faster onset of pain relief than oxycodone tablets, but the duration of analgesia was approximately the same (4 hours). However, the incidence of side effects and their severity were significantly higher (p < 0.05) for intravenous oxycodone than for oxycodone tablets. The marked interindividual variation observed in the pharmacokinetics and pharmacodynamics of oxycodone in this study supports the need for individualized dosing regimens.