Enantiospecific pharmacokinetics and pharmacodynamics of ketoprofen in sheep

Pharmacokinetic and pharmacodynamic parameters were established for the ena ntiomers of the 2-arylpropionic acid (APA) nonsteroidal anti-inflammatory d rug (NSAID), ketoprofen (KTP). Each enantiomer was administered separately (1.5 mg/kg) and in a racemic mixture (3 mg/kg) intravenously (i.v,) to a gr oup of eight sheep in a four-way, four-period cross-over study using a tiss ue cage model of inflammation. Plasma disposition of each KTP enantiomer wa s similar following separate administration of the pure compounds compared to administration of the racemic mixture. S(+)KTP volume of distribution (V d(area)) was higher and clearance (C/(B)) faster than those of R(-)KTP.S(+) and R(-) KTP achieved relatively low concentrations in exudate and transud ate. Unidirectional limited chiral inversion of R(- to S(+)KTP was demonstr ated. After R(-)KTP administration S(+)KTP was detected in plasma, but not in either exudate or transudate. Pharmacokinetic/pharmacodynamic (PK/PD) modelling of the data could not be undertaken following R(-)KTP administration because of chiral inversion to S(+)KTP, but the pharmacodynamic parameters, calculated maximum effect (E-m ax), concentration producing 50% effect (EC50), Hill's coefficient (N), rat e constant of elimination of drug effect from the compartment (Ke0) and mea n equilibration half-life (t1/2 KeO) were determined for S(+)KTP after admi nistration of the racemic mixture as well as the pure compound.