Comparison of the bioavailability of dexibuprofen administered alone or as part of racemic ibuprofen.

Two bioavailability studies of S(+)-ibuprofen (dexibuprofen) were conducted in healthy volunteers to define the relationship between the bioavailability 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 dexibuprofen from a 400 mg tablet formulation was compared with that from 400 mg in aqueous solution. The tablet formulation did not influence the bioavailability of the drug and dexibuprofen was well absorbed from the gastro-intestinal tract. The second study was divided into three identical parts. Bioavailability of dexibuprofen 200, 400 and 600 mg was compared with its bioavailability from ibuprofen racemate 400, 800 and 1200 mg. The second study showed that the mean relative bioavailability of dexibuprofen to ibuprofen racemate was 0.66, thus enabling the estimation of clinically useful dexibuprofen doses from the usual doses 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 therapeutically active drug.