An open-label pharmacokinetic study of oxymorphone extended release in the presence of naltrexone in the older adult.

Objective: The aging population generally has greater need for analgesics and is best served by having as many good therapeutic options as possible. Geriatric analgesia requires special consideration of age-associated physiologic changes that can affect drug dosing. The study of extended-release (ER) oxymorphone in older (≥ 65 years of age) versus younger (18-40 years of age) male and female volunteers was described.

Methods: In this multiple-dose, parallel-group, open-label trial, healthy volunteers received a single oral dose of 20 mg oxymorphone ER on day 1, followed by a 48-hour washout period, then two oral doses of 20 mg oxymorphone ER tablets every 12 hours from day 3 to day 8, and a single oral dose of 20 mg oxymorphone ER on day 9. Naltrexone was administered each day to the subjects.

Results: The elderly had significantly higher plasma levels of oxymorphone, 6-OH-oxymorphone, and oxymorphone-3-glucuronide than the younger group (1.36-fold higher area under the concentration versus time curve [AUC] and 1.45-fold higher C(max)) when they were treated with a single dose (20 mg) of oxymorphone. Steady-state AUC and C(max) also were higher in the older group. Following adjustment for body weight, AUC values for oxymorphone and its metabolites were about 40 percent higher and the mean C(max) values were 30-35 percent higher in the older group compared to the younger group.

Conclusion: The results of the current study of an ER formulation revealed no pharmacokinetic features that would preclude dosing in the elderly. As with any drug and any age group (but particularly the elderly), oxymorphone ER should be initiated at lower doses in elderly compared to younger patients and titrated to optimal level.