Abstract
Newly developed simultaneous extraction and quantitation methods for oseltamivir phosphate (OP), oseltamivir carboxylate (OC) and zanamivir hydrate (ZH) were used to monitor the drugs in upstream section of Neya River water in Osaka during the last three consecutive influenza seasons (2009/2010, 2010/2011 and 2011/2012). High concentrations of the drugs (particularly for OC) were observed in the water in the three seasons. Influenza index values, defined as average number of reported influenza cases per hospital within the coverage area during a week, were also calculated. Strong direct correlations between the index values and measured drug concentrations in the water (particularly for OC) indicated that influenza index values may be used in estimating concentrations of anti-influenza drugs in receiving waters in seasonal influenza. An ecological risk assessment indicated that the antiviral drugs at concentrations observed in Neya River water may not have negative impacts to the environment except in pandemic influenza cases. These findings can be a useful reference for other similar cases and for further investigations.
