Determination of the retinobenzoic acid derivative Am580 in rat plasma by high-performance liquid chromatography

A specific liquid chromatographic method for the determination of 4-[[(5,6,7,8,8-tetrahydro-5,5,8,8-tetramethyl-2- naphthalenyl)carbonyl]amino]benzoic acid (Am580) in rat plasma is described. The procedure includes one-step isolation of the compound and the internal standard (naphthol AS) from protein precipitated with acetonitrile, resolution on a reversed-phase column (Supelcosil LC18-DB, 5 microns) with water-acetonitrile-methanol-n-butanol (45:40:14:1, v/v) containing 65 mM ammonium acetate as elution system and UV absorbance detection at 280 nm. The assay was linear over a wide range (25-5000 ng ml-1) and the limit of quantitation was 25 ng ml-1 using 0.2 ml of plasma. It was precise and reproducible enough for pharmacokinetic studies. Application to a preliminary disposition study in the rat indicated that Am580 was characterized by a relatively large apparent volume of distribution (1.1-1.5 1 kg-1) and small clearance (8.8-9.7 ml min-1 kg-1). Its pharmacokinetic behaviour was linear within the dose range considered (2 and 10 mg kg-1, i.p.).