HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC (HPLC) DETERMINATION OF LOBENZARIT IN PLASMA AND ITS APPLICATION TO A BIOAVAILABILITY STUDY IN BEAGLE DOGS

A method for the quantitative determination of lobenzarit (2-[(2-carboxyphenyl)amino]-4-chlorobenzoic acid) in dog plasma by high-performance liquid chromatography with UV detection (308 nm) is described. Plasma samples (200-mu-l) were treated with acetonitrile and centrifuged, and the clear supernatant injected onto a reversed-phase phenyl column. The method achieved a limit of quantitation of 0.5-mu-g/ml in plasma, and the response was linear to 100-mu-g/ml. Comparing a solution and a tablet formulation given to beagle dogs, the assay demonstrated that the solution formulation was slightly more bioavailable and yielded a more variable absorption rate. The elimination of lobenzarit from plasma followed a biexponential time course, with an apparent terminal disposition half-life of between 5.8 and 10.7 hr.