Repeated Oral Administration of Ivermectin Belatedly Induces Toxicity and Disrupts the Locomotion and Neuropsychiatric Behavior in Rats

Abstract

In 2020, the World Health Organization declared that COVID-19, caused by the SARS-CoV-2 virus, is a pandemic. This led to severe respiratory syndromes and overwhelmed hospital capacities alongside the widespread, yet unproven, use of drugs like ivermectin. Amidst growing concerns over the consequences of frequent ivermectin use, this study aims to examine its toxicological effects following repeated dosage in rats. Female Wistar rats received a daily dose of 12 mg/kg of ivermectin intragastrically for 5 days. Two groups were studied: one euthanized 24 h post the final dose (early protocol) and the other 14 days later (late protocol). The rats underwent tests for locomotion and anxiety- and depression-like behaviors. Additionally, blood and cortex samples were analyzed for acetylcholinesterase and Na+/K+-ATPase activities, oxidative stress levels, and liver and kidney function markers. The early protocol results showed decreased locomotion and increased signs of anxiety and depression in the rats, along with Na+/K+-ATPase inhibition and oxidative stress. In the late protocol, signs of persistent depression-like behavior and hyperlocomotion were observed, coupled with heightened oxidative stress, as indicated by increased reactive oxygen species and disrupted catalase activity. Moreover, the dual inhibition of acetylcholinesterase and Na+/K+-ATPase activities seems to underlie the behavioral alterations seen in the late protocol. The study also noted ivermectin's potential hepatotoxic effects, corroborating previous findings of elevated liver enzyme levels and severe drug-induced liver injury cases, as well as delayed neuropsychiatric and behavioral changes.

Figure 1

Experimental design of the early and late protocols.

Figure 2

Effects of ivermectin treatment on rat locomotor function in the open field test. (A) Number of crossings and (B) number of rearings in the open field test. Data are expressed as mean ± SEM (n = 10 animals per group). The data were analyzed using the unpaired Student t test. **p < 0.01 and ***p < 0.001 indicate a significant difference compared to the control group.

Figure 3

Effects of ivermectin treatment on rat anxiety-like behavior in the elevated plus maze test. (A) Total time in the open arm; (B) number of dives; (C) number of crossings performed by the rats. Data were expressed as mean ± SEM, with 10 animals per group. The data were analyzed using the unpaired Student t test. *p < 0.05 indicate a significant difference compared to the control group.

Figure 4

Effects of ivermectin treatment on rat anhedonic and depressive-like behavior observed in the splash test and forced swim test. (A) Time of grooming in the splash test and (B) immobility time in the forced swim test. The data are expressed as mean ± SEM, with n = 10 animals per group (Figure A); 6 animals per group (Figure B). Analysis was conducted using the unpaired Student t test. *p < 0.05; **p < 0.01 and ****p < 0.0001 indicate a significant difference compared to the control group.

Figure 5

Effects of ivermectin treatment on (A) AChE and (B) Na⁺, K⁺-ATPase activities in the prefrontal cortex of rats are presented. Values are expressed as the mean ± SEM, with n = 8–10 animals per group (Figure A); 10 animals per group (Figure B). Data were analyzed using the unpaired Student t test. *p < 0.05, **p < 0.01, and ***p < 0.001 indicate a significant difference compared to the control group.

Figure 6

Effects of ivermectin treatment on (A) CAT activity and (B) ROS levels in the prefrontal cortex of rats. The values are presented as the mean ± SEM, with n = 8–10 animals per group (Figure A); 10 animals per group (Figure B). The data were analyzed using the unpaired Student t test. *p < 0.05, **p < 0.01, and ***p < 0.001 indicate a significant difference compared to the control group.