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Study: Discarded drugs could pose threat to fish

Anxiety medicine changes behavior

What happens to a fish on drugs?

If it’s a wild European perch exposed to a popular anxiety medication, chances are it’s antisocial, wanders away from the safety of its group and devours food more quickly than its peers – all behaviors that could have profound ecological consequences, according to a forthcoming report in the journal Science.

In a study aimed at further understanding the environmental impacts of pharmaceuticals that often wind up
in the world’s waterways through wastewater, researchers from Umea University in Sweden examined how perch behaved when exposed to oxazepam, a drug commonly used to treat anxiety disorders in humans. The scientists exposed the fish to concentrations of the drug similar to those found in the waters near densely populated areas in Sweden.

The result?

“Normally, perch are shy and hunt in schools. This is a known strategy for survival and growth. But those who swam in oxazepam became considerably bolder,” said ecologist Tomas Brodin, leader author of the article. They “lost interest in hanging out with the group.”

Brodin told an audience at the American Association for the Advancement of Science meeting in Boston yesterday that researchers conducted a “boldness test” on the perch, opening a door that would allow them to swim from a small box into a much larger water tank. The fish with no drugs in their system remained timid and “didn’t come out at all,” he said, while those on oxazepam did.

“We think it’s working through stress relief on the fish,” Brodin said. “It removes the fear of being eaten.”

The researchers said those behaviors, coupled with the tendency to scarf down food faster than normal, could alter the composition of the species and lead to ecological changes in the real world. For example, if they consumed more plankton, it could lead to an increase in algae.

Although Brodin and his colleagues focused on oxazepam in their research, they
noted that residue from a “veritable cocktail of drugs” can
be found in waterways worldwide.

Past studies have confirmed that an ever-growing cocktail of pharmaceuticals and
other pollutants – including shampoos, perfumes, heart medications, painkillers and birth control pills – exists in waterways across the globe. There has been scant evidence thus far that the chemical traces pose any dangers to humans, but researchers have plenty to learn.

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