Antidepressants in the environment: combatting pharmaceutical pollution

Around six million people in the UK – roughly 10% of the population – now regularly take antidepressant medication such as Prozac (fluoxetine) and the figure has doubled in the last decade. Detectable levels of these drugs, and other commonly used medications, have been found in the UK’s sewage, drinking water, rivers, coastal waters and animal tissues, and pose a potential threat to natural habitats and ecosystems. Pharmaceutical pollution is a major concern for environmental toxicologists with the widespread use of psychotropic medication a particular issue in high-income countries.

In a recent abstract for the British Journal of Psychiatry, experts at the University of Portsmouth have called for prescribers of antidepressants (GPs and healthcare professionals) to consider the wider implications of antidepressant use.

Professor Alex Ford, a biologist at the university and an expert in the effects of human waste on marine life says: “There is much debate about the overprescribing of antidepressant medication and hence we wanted to include an environmental aspect to that debate.”

His colleague Dr Helena Herrera, an expert in ethical pharmacology, adds: “There is a large interest within publicly funded health systems to reduce the use of medicines, both to reduce unnecessary costs and adverse effects. While these drugs have a clear place in therapy, there is debate around the risk/benefit ratio in patients with mild mental health problems. Therefore it is necessary to evaluate the wider implications as risks could extend beyond the individual to non-target organisms, particularly those in rivers and estuaries.”

The first reports of commonly prescribed drugs being found in the marine environment were in the 1960s, but it was 30 years before scientists had evidence that the contraceptive pill and hormone replacement therapy drugs in waste water could feminise fish. Since then, a growing body of research has revealed that pharmaceutical pollution is a potential threat to ecosystems, with antidepressants and anti-anxiety drugs now garnering particular interest from environmental toxicologists.

Antidepressants generally act on neurotransmitters and their transporter proteins in humans. These neurohormones and transporters are also found extensively throughout the animal kingdom, and hence, any drug designed to alter the biology of a human will also alter the biology of wildlife.

“Neurotransmitters such as serotonin and dopamine not only control behaviour as they do in humans, but also many other biological functions in animals especially invertebrates,” explains Ford. “Laboratory studies are reporting changes to growth, immunity, reproduction, metabolism, feeding habits, movement and even to the capacity to change colour. This isn’t about a one-off pollutant entering their habitat; wildlife are bathed in drugs for their entire lifecycle.”

Another key point is educating patients to return their waste medication to the pharmacy where it can be safely disposed of, rather than flushing it down the toilet or throwing into the rubbish bin where, in landfill later, it can leech into ground water.

“This depends on the country as to whether the pharmacy disposal service is free,” continues Ford. "There have been calls in some US states for the pharma industry to pay for the ‘take back’ programmes.”

Finally, the pharmacological industry needs to move towards a ‘cradle-to-grave’ approach with drugs that are designed and dispensed, by making it easier for them to be safely broken down. However, development of biodegradable drugs isn’t straightforward.

"It's very difficult for pharma to create ‘green’ pharmaceuticals,” concludes Ford, “as the properties required to keep them stable in the body are precisely the opposite to that required to break down in the environment.”