Evaluation of the potential environmental risk from the destination of medicines: an epidemiological and toxicological study.

Background: The high consumption of medicines by the population and their storage at home might cause an increase in the number of pharmaceutical substances that may be inappropriately discarded in the sanitary sewage, reaching an environmental aquatic. Thus, the effects of these emerging contaminants need more studies.

Objectives: To identify the profile of most medicines that are discarded by users of community pharmacy and evaluate the toxicity of the most disposed drugs.

Methods: This was a translational study. A descriptive observational study was carried out for convenience of community pharmacy users using a standardized questionnaire. Subsequently, the lethal concentration 50 (LC₅₀) for medicine that is most frequently discarded was determined. After LC_50, the embryos (n = 144) were exposed to sublethal concentrations for most discarded drug at 24, 48, and 72 h. Mortality, heartbeat, and embryo deformities were used as parameters of toxicity.

Results: Most respondents (96%) had a "home pharmacy." The primary forms of disposal were in the common household waste, kitchen sink, and/or bathroom. The medicines that were most incorrectly discarded by the interviewees were nimesulide (17.1%), dipyrone (10.7%), and paracetamol (5.2%). LC₅₀ of nimesulide was calculated (0.92 μgmL^-1). The toxicological test revealed that embryos exposed to nimesulide showed several abnormalities, such as defects in the spinal cord, tail, yolk sac, as well as pericardial edema. Furthermore, the heartbeat decreased by 30% at a concentration of 0.4 μgmL^-1 as compared with control group. The yolk sac and pericardial areas increased to >100% in all treatment groups when compared with the control group.

Conclusion: Respondents disposed medicines in an inappropriate manner primarily in household waste and in the toilet. Nimesulide was the most discarded drug according to study population. Moreover, teratogenic effects such as spinal cord defects, decreasing heartbeats, and increasing pericardial and yolk sac area in embryos were observed after exposure to nimesulide. These results show that nimesulide may promote risk to aquatic organisms and to human health if it is discarded in an unsafe manner.