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Flunoxaprofen is a new nonsteroidal antiinflammatory agent that, like benoxaprofen, inhibits leukotriene rather than prostaglandin synthesis. The absorption and disposition kinetics of flunoxaprofen and benoxaprofen have been compared in six healthy volunteers after oral administration of 100 mg of each drug. The two drugs showed similar absorption characteristics, whereas the distribution and elimination processes were much faster for flunoxaprofen. The renal route of elimination appeared to contribute significantly less to the disposition of flunoxaprofen. These kinetic characteristics render less likely the risk of excessive drug accumulation with flunoxaprofen, especially in the presence of reduced renal function.

The absorption and disposition kinetics of the enantiomers of the nonsteroidal antiinflammatory drug flunoxaprofen were studied in six healthy volunteers after oral administration of either R,S(+/-)-flunoxaprofen or R(-)-flunoxaprofen. The apparent values of the volume of distribution and systemic clearance of the S(+)-enantiomer were significantly lower than those of the R(-)-enantiomer. There was no significant difference in the absorption and elimination half-lives between the two isomers. The S(+)- to R(-)-isomer plasma concentration ratio increased with time with an apparent inversion half-time of about 50 h. This observation suggests metabolic inversion of R(-)- to S(+)-enantiomer, although the possibilities of stereoselective bioavailability or interaction between the two isomers can not be excluded.

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.