Dissipation of the of the antiviral drug oseltamivir (Tamiflu) in surface water

Several studies have shown that a wide number of pharmaceuticals used in human and veterinary medicine have the potential to enter the aquatic ecosystem. The antiviral prodrug oseltamivir phosphate (OP) has received recent attention with regard to its possible use against the highly pathogenic H5N1 virus. This laboratory study investigated the persistence of the active antiviral drug oseltamivir carboxylate (OC) in water samples from an irrigation canal. OC was moderately persistent in surface water samples. Approximately 65% of the initial OC amount remained in water at the end of the 36-day incubation period. A relatively small amount of OC was lost both from sterilized water and from sterilized water/sediment samples, suggesting a significant role for microbial degradation. Stimulating microbial processes by the addition of sediments resulted in reduced OC persistence. The presence of moderate concentration of OC (1.5 Xg mL-1) did not significantly affect the metabolic potential of the water microbial population, estimated by glyphosate and metolachlor mineralization. In contrast, OC caused an initial transient decrease of the size of the indigenous microbial population of water samples.