Pharmacokinetic studies of benoxaprofen in geriatric patients.

Benoxaprofen plasma profiles were obtained in 10 elderly patients (mean age 77 years) suffering from osteoarthritis and various underlying diseases. Blood levels were measured over a 17-day period. Benoxaprofen, 600 mg, was given daily for the first 10 days. The mean peak plasma concentration on Day 1 occurred three hours after the fasting dose. Mean plasma levels on Days 2-10 showed a continuing rise with no indication that a steady-state level was achieved. Elimination half-lives calculated from plasma levels on Days 12-17 resulted in a mean of 101 hours in these elderly patients. This is a substantial increase compared with normal subjects (half-life 30 to 35 hours). Most haematologic and biochemical results were judged to be within the usual range for this type of elderly patient (A.K.) No evidence of renal impairment due to the treatment was shown. The higher benoxaprofen concentrations and the long elimination half-life show evidence of accumulation in the elderly, probably due to several causes, including poor bowel motility and decreased renal clearance common with increasing age. The recommended dose may require modification in geriatric patients.