Toxicological effect of acetaminophen, metamizole, and nimesulide cocktail on early development of zebrafish.

Background: Several countries' most incorrectly discarded medicines are acetaminophen (ACM), metamizole (MTZ), and nimesulide (NMS). These xenobiotics easily reach the aquatic environment; such contamination is very important for the health of humans and other species, yet little explored.

Objectives: To evaluate the cocktail effect of ACM, MTZ, and NMS during zebrafish's initial development.

Methods: Zebrafish embryos 6-8 h post-fertilization (hpf) were exposed to different concentrations of ACM, MTZ, and NMS, separately, to obtain the 50% lethal concentrations (LC₅₀). Next, the embryos were exposed to distinct concentrations of the cocktail (LC₅₀/2, LC₅₀/5, LC₅₀/10, and LC₅₀/20) in a semi-static system. Samples were analyzed 0, 24, 48, and 96 h after exposure, and the drugs' concentrations in E3 medium were assessed by high-performance liquid chromatography. For embryotoxicity evaluation, the mortality, hatching, and heart rates; total length; and pericardial and yolk sac areas were determined. In addition, body malformations, edemas, presence of pigmentation, and histopathological assessments were also recorded.

Results: The LC₅₀ values obtained for MTZ, ACM, and NMS were 4.69 mgmL^-1, 799.98 μgmL^-1, and 0.92 μgmL^-1, respectively. No difference was observed between the drugs' nominal and observed concentrations at each time point. The cocktail significantly induced mortality and decreased hatching in the LC₅₀/10, LC₅₀/5, and LC₅₀/2 groups. Additionally, body malformations, pigmentation loss, and yolk sac and pericardial edemas were observed in the cocktail groups. The cocktail groups' larvae had decreased total length and slower heart rates compared to the controls (p < 0.05). The histopathological assessment showed that yolk sac edema promoted severe histological changes in the esophageal-intestine junction and intestine in larvae treated with cocktails. Moreover, PAS-positive structures decreased in the esophageal-intestine junction, intestine, and liver in larvae exposed to pharmaceutical cocktails.

Conclusion: This study's findings suggest the cocktail of ACM, MTZ, and NMS may be hazardous to aquatic organisms in case of environmental contamination.