Bugs can convert drugs into deadly toxins

Last Updated: Dec 05, 2011, 13:34 PM IST

Sydney: Bugs can convert traces of drugs, present in sewage, into deadly toxins, especially during the water treatment process. The process mimics a similar transformation in the human gut, where drugs believed to be safe can be converted into toxic forms during metabolism.

University of New South Wales (UNSW) researchers monitored three common drugs during wastewater treatment, the journal Water Research reports. These included the anti-inflammatory drug naproxen, which is manufactured and dispensed as S-naproxen.

Its counterpart, R-naproxen, is known to be highly toxic to the liver and is not publicly available, according to New South Wales statement. Through the treatment process, researchers observed that some of the safe version of naproxen had been converted to the unsafe form.

The two are an example of enantiomers - drugs that can occur in two forms. While they are chemically very similar, pairs of enantiomers can have drastically different effects on the human body, from medically beneficial to highly toxic.

"We found that some of the S-naproxen had turned into R-naproxen," says study supervisor Stuart Khan, environmental engineer at the UNSW Water Research Centre.

This is the first time that enantiomeric inversion during the wastewater treatment process has been reported.

The most famous case of such inversion is that of thalidomide, a drug designed to control morning sickness that was administered to pregnant women in the late 1950s. It is not well understood how this transformation is occurring in wastewater, but is believed to be enzyme-driven, says Khan.