A NOVEL SIMULTANEOUS HPLC ASSAY FOR SERUM PARACETAMOL AND SULFAPYRIDINE AS MARKERS OF GASTRIC-EMPTYING AND OROCECAL TRANSIT

A simple high-performance liquid chromatography method is described fo r the simultaneous determination of two marker drugs, namely paracetam ol and sulfapyridine, in serum, indirectly indicative of gastric empty ing and orocecal transit, respectively. Extraction of the drugs from s erum was achieved with chloroform:isopropyl alcohol (7:3). Analysis wa s performed with a mobile phase comprising 1.9% tetrahydrofuran in 0.0 1 M sodium acetate buffer adjusted to pH 4.5, through a YMC-Packed C18 column at a flow rate of 1.0 ml/min and ultraviolet detection at 254 nm. The detection limit is approximately 0.2 mu g/ml for paracetamol a nd 0.1 mu g/ml for sulfapyridine. This method is applicable to monitor ing gastric emptying and orocecal transit following oral administratio n of paracetamol and sulfasalazine, the latter being hydrolyzed in the large bowel and absorbed as sulfapyridine.