Pharmacokinetics of the enantiomers of tiaprofenic acid in humans.

A gas chromatographic method was utilized to study stereoselective pharmacokinetics of the nonsteroidal anti-inflammatory drug, tiaprofenic acid (5-benzoyl-alpha-methyl-2-thiopheneacetic acid), in four arthritic patients receiving 200 mg/8 h of the racemic drug. Synovial concentrations of the enantiomers were also measured following administration of single 200-mg doses of the drug to six other patients. In the analytical procedure, racemic tiaprofenic acid was coupled to (S)-(+)-amphetamine and the corresponding diastereoisomeric amide derivatives were resolved. Analysis of serial blood and urine samples at steady state, and single synovial samples, revealed that tiaprofenic acid enantiomers had superimposable plasma concentration-time and urinary excretion-time profiles and equivalent synovial concentrations. These results indicate that, unlike most 2-arylpropionic acid anti-inflammatory drugs, tiaprofenic acid enantiomers do not have different disposition kinetics, and the metabolic chiral inversion of one to the other does not occur or is so slow that the drug is eliminated before significant inversion takes place.