Bioinversion of ibuprofen enantiomers after administration in dogs: estimation of a novel index

This study compares the pharmacokinetics and bioinversion of two chemical forms of ibuprofen administered intravenously or orally. Dogs were given the free acid form of the S(+) isomer p.o. or i.v., or the racemate, as the free acid or sodium salt, p.o., in a cross-over design. The main kinetic parameters were calculated and formation and bioinversion curves plotted. The values of Cmax, Tmax and AUC were higher for the S(+) isomer. The percentage bioinversion averaged between 35-70% according to the form. This study proposes a new index for the calculation of bioinversion, independently of any i.v. administration, and confirms its self-limiting nature.