Determination of ibuproxam and its metabolites in the plasma and urine of rats.

The metabolism of 2-(4-isobutylphenyl)-propio-hydroxamic acid (ibuproxam, Ibudros), a new molecule with anti-inflammatory, antipyretic and analgesic activity was studied by its administration orally and rectally to the rat. The analysis, carried out with gas chromatographic method and thin-layer chromatography, showed that the drug is present in blood as 2-(4-isobutylphenyl)-propionic acid (ibuprofen), an anti-inflammatory drug which is commonly used and the metabolites of which are already known. Using the same methods, it was observed that only a few traces of the hydroxamic acid appear in the urines of rats treated with ibuproxam, whilst the ibuprofen metabolite is absent. Therefore, we conclude that the drug ibuproxam changes rapidly into ibuprofen, following afterwards the same known metabolic process as the latter drug.