Nootropic drugs: Methylphenidate, modafinil and piracetam - Population use trends, occurrence in the environment, ecotoxicity and removal methods - A review

Pharmaceuticals which originally were designed to treat people with neurological and psychiatric conditions, e.g. Alzheimer's disease or attention deficit hyperactivity disorder (ADHD), are nowadays often misused by students as a 'brain doping' substances. These substances are known as nootropic drugs, smart drugs or cognitive enhancers, as they increase memory, attention and concentration of healthy individuals. Since they are easily available illicitly, their consumption is observed to be growing. Currently, these pharmaceuticals started gaining researchers' attention, especially since they have been recently detected in wastewater, surface water and even drinking water. This review summarises the current state of knowledge on nootropic drugs in terms of their population use trends and ethics, occurrence in the environment and detection techniques, toxicity and removal methods, in example of methylphenidate, modafinil and piracetam - three most popular nootropics. It points out that the main sources of knowledge on cognitive enhancers illicit use are often inconsistent questionnaires, which are not supported by wastewater analysis to become more veracious. Simultaneously, the studies concerning toxicity and removal methods of nootropic drugs are still limited and in many cases environmentally irrelevant. Although the prescription rules has been subjected to more strict control in developed countries, regulatory frameworks with regard to their ecosystem occurrence are still lacking and should be introduced. Moreover, the use of environmentally relevant concentrations in toxicity studies should be a standard, leading to proper ecotoxicity risk assessment. Based on this review, it is recommended to routinely monitor nootropics and their metabolites in waste- and surface waters. (C) 2019 Elsevier Ltd. All rights reserved.