Steady-state pharmacokinetics of extended-release hydromorphone (OROS hydromorphone): a randomized study in healthy volunteers.

The steady-state pharmacokinetics of an extended-release formulation of hydromorphone, OROS hydromorphone, was investigated in a randomized, open-label, crossover study in healthy volunteers. Participants were randomly assigned to receive 16 mg of OROS hydromorphone once daily and 4 mg of immediate-release hydromorphone four times daily for five consecutive days. The two treatments were separated by a washout period of 7-14 days. Naltrexone was given throughout both treatment periods to block the opioid effects of hydromorphone. Steady-state hydromorphone concentrations were statistically analyzed using Helmert contrasts to determine when steady state was reached. A total of 30 participants were enrolled, of whom 29 completed both treatment periods. The two treatments produced comparable steady-state plasma drug concentrations, but peak-to-trough fluctuations were smaller with OROS hydromorphone (61 percent vs 172 percent) in comparison with immediate release hydromorphone. Overall systemic exposure to hydromorphone was similar between the two formulations. The ratio of the geometric means between the two formulations for the area under the concentration-time curves at steady state was 105.2 percent with a 90% confidence interval (CI) of 99.8-110.8 (geometric mean: 102.7 percent; 90% CI: 97.6-108.2 after correcting for measured drug content), which was within the bioequivalence range (80-125 percent). The analysis of Helmert contrasts showed that steady state conditions were attained by day 4. Both treatments were well tolerated. This study shows that OROS hydromorphone maintains steady-state plasma drug concentrations within the same range as immediate-release hydromorphone at the same total daily dose, with less fluctuation.