Flunoxaprofen pharmacokinetics in elderly subjects.

Plasma kinetics and 24 h urinary elimination of flunoxaprofen, a nonsteroidal antiinflammatory drug, were studied in 23 elderly patients (mean age 69.9 years) and compared with the data obtained in four young volunteers. The drug was administered as a single oral 100 mg tablet and its plasma and urine concentrations were assayed by a high performance liquid chromatography method. Plasma kinetics fitted a 3-exponential equation with a mean half-life of 7.9 +/- 2.17 hours and a mean peak plasma of 8.5 +/- 2.97 micrograms/ml, which was observed at about the second hour. The values of the areas under the curves (AUC) and the values of total clearance (multiplied by the bioavailability) showed great variability, due to the large differences in the patients body weights; in fact the value of AUC was linearly correlated to the dose divided by the body weight. The mean residence time (MRT) of the drug in plasma was equal to 12.81 h. Low amounts of unmodified drug (about 10%) were found in 24 h urine sample, indicating a high degree of biotransformation. Small differences only were found in plasma kinetics of flunoxaprofen among the present group of elderly patients and the group of four young volunteers; the main difference corresponded to a slower rate of gastrointestinal absorption and to a longer mean residence time.