HPLC determination of benzydamine and its metabolite N-oxide in plasma following oral administration or topical application in man, using fluorimetric detection.

A method for the extraction and quantification of benzydamine and its metabolite N-oxide by liquid chromatography with fluorescence detection in plasma samples is described. This method has adequate sensitivity, specificity and is reproducible. The use of the extraction column allowed a recovery of both benzydamine and its metabolite of over 97% to be obtained. The plasma levels of benzydamine and its metabolite N-oxide were studied after oral administration as sugar-coated tablets or topical application to the vaginal mucosa as a cream to 6 healthy volunteers. After topical application, the plasma concentrations of the unchanged drug and its metabolite are lower than those obtained following oral administration. These data further stress the concept that, whenever possible, topical use should be considered the treatment of choice since, along with a more selective therapy, the incidence of systemic side effects can be considerably reduced.