COMPARISON OF THE BIOAVAILABILITY OF DEXIBUPROFEN ADMINISTERED ALONE OR AS PART OF RACEMIC IBUPROFEN

Two bioavailability studies of S(+)-ibuprofen (dexibuprofen) were cond ucted in healthy volunteers to define the relationship between the bio availability of the drug after administration of dexibuprofen alone or as part of ibuprofen racemate. Enantioselective plasma drug analysis was used throughout. In the first study, the bioavailability of dexibu profen from a 400 mg tablet formulation was compared with that from 40 0 mg in aqueous solution. The tablet formulation did not influence the bioavailability of the drug and dexibuprofen was well absorbed from t he gastro-intestinal tract. The second study was divided into three id entical parts. Bioavailability of dexibuprofen 200, 400 and 600 mg was compared with its bioavailability from ibuprofen racemate 400, 800 an d 1200 mg. The second study showed that the mean relative bioavailabil ity of dexibuprofen to ibuprofen racemate was 0.66, thus enabling the estimation of clinically useful dexibuprofen doses from the usual dose s of the racemate. The 95% confidence interval limits did not include 0.5, leading to the conclusion that administering half of the racemate dose would not provide patients with an adequate amount of therapeuti cally active drug.