Swedish researchers have published a paper reporting a drug commonly used to treat anxiety in people has been shown to reduce mortality rates in fish.

The findings may have noteworthy implications for current standard ecotoxicological tests geared towards detecting the awful side effects of contaminants in water while dismissing potentially good side effects.

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Researchers said the drug Oxazepam could change the equilibrium of a species in an ecosystem by improving the health of aquatic organisms. The change, however, could lead to consecutive ecological repercussions, according to the scientists from the Umeå University in Sweden.

Dr. Jonatan Klaminder, lead author of the paper, said current ecotoxicological studies were conducted with common poisonous contaminants in mind. Among these contaminants are dioxins and heavy metals that are the dominant dangers to aquatic organisms in shallow waters.

"Pharmaceuticals, which are designed to improve health, are a new group of contaminants that do not necessarily fit into the traditional view," Klaminder said.

"I think there is a 'bandwagon effect' within the research community where the old test and the traditional view of a contaminant is routinely used without reflection about the conceptual flaw implicit in the methods."

In the experiment, scientists recovered two-year-old Eurasian perches from a lake in Sweden and exposed them randomly to low and high concentrations of Oxazepam.

Oxazepam is a benzodiazepine usually given to suppress insomnia and anxiety in people. It often contaminates shallow waters through filtered sewage and wastewater.

Scientists have shown the drug can enhance the boldness and activity of the sample species.

The concentration of the drug in the study was lower than levels in the treated waters in Europe.

Eggs from a separate population of the fish were also collected and exposed to the three concentrations of the drug during the first nine days of embryonic development. A random group of hatchlings were gathered and analyzed

The mortality rate among the wild hatched fry was high and relatively high among two-year-old perch. The exposure of the treated populations to Oxazepam led to a lower mortality rate compared to the control group.

Tomas Brodin, the team ecologist and co-author of the paper, said the healing effect of the drug that leads to the preservation of one of the members of the ecosystem may generate an equivalent decrease in the population of the species' prey.

The imbalance in the ecosystem may lead to repercussions that need to be considered.

The team said the traditional view of pollutants has blocked them from experimenting for similar side-effects at concentrations relevant to the environment.

TagsDrugs, medicine, Ecosystem, Research, Runoff