Evaluation of the virucidal effect by contact with water-insoluble substances: the case of Xibornol

The virucidal activity of xibornol has been known since the 70s, but its determination is primarily based on few clinical data. Experimental quantitative estimation in vitro is limited by the absence of appropriate test neither the European nor the American Pharmacopoeia; however some recent standards, concerning antiseptics, could be utilized for this purpose. The tests were carried out by following the European Standard EN 14476, which foresees contact test between viruses and 3 different concentrations of xibornol, in two experimental conditions and viral titer estimation by cell culture method. The tested viruses were chosen among those ones most closely responsible of upper respiratory tract infections: Human Adenovirus, Human Rhinovirus and Human Corona virus. For the commercial concentration (3%), the results show a common trend for all the viruses with an estimated titer that reached values below 1 log DCP50/ml after each condition contact test. The reduction was greater in clean conditions with average value of 3 logs, compared to the test in dirty conditions (2 log). The data confirm the virucidal action of xibornol and show, for the first time, a quantitative variation in disinfection efficiency depending on contamination scenario.