Physiological and Biochemical Responses to Repeated Administration of Ivermectin in Rabbits

Introduction

Ivermectin is a semisynthetic derivative of a vermectin, a naturally occurring macrocyclic lactone produced by the bacterium Streptomyces avermitilus (Hazan, 2022). This lipophilic endotoxin exhibits broad -spectrum antiparasitic activity and is widely employed in both veterinary and human health managements to control nematodes, arthropods, and other parasitic infections (Hasan et al., 2022). Ivermectin is commonly used in animal husbandry systems for the prevention and treatment of infections caused by internal parasites in horses, cattle, sheep and goats (Parisi et al., 2019; Bordes et al., 2020; Ahmed et al., 2020). Due to its wide use, the physiological and pharmacological effects of ivermectin on target species remain the subject of ongoing research. Ivermectin is the only avermectin derivative authorised for use in humans and is effective against parasitic infections such as onchocerciasis and lymphatic filariasis. Its pharmacological action is thought to be mainly mediated by modulation of glutamate-gated chloride channels in invertebrate nerve and muscle cells, resulting in increased chloride flow, hyperpolarisation of the membrane, paralysis and ultimately death of the parasites (Wolstenholme and Neveu, 2022).

Importantly, ivermectin has a broad margin of safety in mammals, since these channels are not present in vertebrate neurons and its effect on mammalian (gamma-aminobutyric acid-mediated chloride) channels at therapeutic doses is negligible (Shwaish et al., 2024). Despite its proven efficacy and extensive therapeutic use, there were concerns about possible adverse reactions in treated animals. Ivermectin exhibits a variety of pharmacokinetic properties, including high solubility of the lipid, long half-life and extensive tissue distribution, especially in the liver and adipose tissue (Hennessy and Alvinerie, 2002). These properties may cause bioaccumulation and delayed elimination, especially via milk excretion during lactation. Ivermectin is also extensively metabolised in the liver by cytochrome P450 (CYP450) enzymes. Experimental studies indicate that ivermectin and its metabolites may inhibit the cytochrome P450 system and related drug transporters in mammals, potentially resulting in hepatocyte damage, metabolic abnormalities and immunotoxic or nephrotoxic effects (Salman et al., 2022).

Several studies have shown that avermectins (ivermectin, abamectin, doramectin and eprinomectin) may cause a variety of biochemical, hormonal and histopathological changes in animals exposed to these substances (GabAllh et al., 2017; Salman et al., 2022). In cattle, prolonged or repeated dosing of these substances, even at therapeutic levels, has been associated with disturbances of endocrine function and reproduction physiology. This includes dysregulation such as hormonal imbalances, altered reproductive patterns and reduced fertility (Sadek and Shaheen, 2015; Nicolas et al., 2020). In view of these observations, further investigation is needed to determine whether ivermectin alters physiological homeostasis. Changes in serum biochemistry, electrolyte balance and oxidative stress parameters may provide critical information on the systemic effects of a pharmacologically active substance and the mechanisms underlying adverse reactions. Based on this, this study looked at the effects of ivermectin in rabbits and the results should further our understanding of the potential toxicological effects of ivermectin and its wider application in the veterinary field.

Material and methods

The study included 10 clinically healthy adult male rabbits (Oryctolagus cuniculus) from the age of 10 to 12 months, weighing 1.5 to 2 kg. The animals were kept in a physiology laboratory at the University of Fallujah under controlled climate conditions (23 ± 3°C, 12 hours of light and dark cycles, and 50-60 % relative humidity). They were provided with a balanced commercial diet and unrestricted access to water. Before the experimental methods, all animals underwent an acclimatization phase of two weeks to minimize handling stress and achieve full acclimatization to the laboratory environment.

After acclimation, rabbits were randomly allocated to one of two groups of five animals: a control group (no treatment) and a group ivermectin (Ivermac-10^®, ADWIA Pharmaceuticals, Egypt) that received subcutaneous administration of 0.25 mg ivermectin once weekly for 4 weeks. Before sampling, animals were lightly anaesthetised with xylazine (6 mg per kg body weight, intramuscular) (Sarwar et al., 2014) to reduce the discomfort of the procedure and blood samples were obtained by cardiac puncture.

All procedures in animals, including anaesthesia and blood sampling, were in accordance with the recommendations of the American Vets Medical Association (Underwood et al., 2013). The blood samples were centrifuged at a rate of 3000 rpm for 10 minutes to obtain a serum sample which was then stored at -20-20°C for further investigation. Serum concentrations of sodium, potassium and chloride were measured with the using a Diasys Respons^® 920 automatic analyser (Diasys Diagnostic Systems, Germany). Biochemical parameters for this study using colorimetric assay Kit (Agape Diagnostics Swtzerland for glucose, total protein, albumin and AST and ALT), (Sam Diagnostic, Dubai-UAE for urea, uric acid, cholesterol and superoxide dismutase activity) and (Biolabo SAS, France for creatinine, triglycerides, MDA and GSH) and (Elabscience, china for calcium, magnesium and phosphate). All data were statistically analyzed using a T-independent test (SPSS category 21) to demonstrate variations among groups. Values were described as means standard error at P ≤ 0.05 (Larsen et al., 1973). All experimental procedures have been carried out in accordance with institutional guidelines on the care and use of laboratory animals.

Results

Discussion

In rabbits, ivermectin induced multiorgan effects primarily via the liver and the kidney. Significant increases in serum sodium, potassium, chloride, and phosphate levels (Table 1) indicate renal tubular dysfunction and electrolyte disturbances. As a highly lipophilic compound, ivermectin accumulates in the liver and kidney, where it interferes with cytochrome P450 enzymes and P-glycoprotein transporters (Rendic, 2021), resulting in oxidative stress, tubular degeneration, and increased activity of hepatic enzymes (El-Far, 2013; Salman et al., 2022; Miranda et al., 2025).

Significant increases in serum glucose, creatinine, triglycerides, cholesterol and total protein after repeated ivermectin administration ( Table 2) indicate concurrent liver and renal injury. Increase in creatinine, however, indicates impaired renal clearance. Adding insult to injury, hyperglycaemia and hyperlipidaemia indicate liver overload and disturbances of both carbohydrate and lipid metabolism (Cao et al., 2025). Coinciding low serum albumin in ivermectin group indicates decreased hepatic synthesis capacity, which is consistent with the high liver enzymes observed below. In addition, metabolic disorders induced by ivermectin are likely mediated by mitochondrial and cellular ATP dependent blockade and by increased gluconeogenesis and lipolysis (Wang et al., 2018).

In addition, ALT, AST and MDA levels increased significantly with a significant decrease in GSH and SOD activity ( Table 3), suggesting that ivermectin may be involved in oxidative stress as a major mechanism of cellular damage (Wang et al., 2023). Increased MDA levels indicate increased lipid peroxidation, which reflects oxidative damage of the translational machinery of the cell. On the other hand, depletion of antioxidant parameters indicates that the innate protection against reactive oxygen species is depleted, leading to damage to the hepatocellular membrane and subsequent leakage of intracellular enzymes such as ALT and AST (Abu Hafsa et al., 2021; Tang et al., 2022; El-Shobokshy et al., 2023). In addition, mitochondrial failure, combined with a decrease in ATP production, increases oxidative stress, which causes severe damage to both liver and kidney tissues (Zhang et al., 2022).

The combination of prolonged oxidative stress and decreased liver and kidney function creates a self-sustaining imbalance that promotes deterioration. Secondary renal dysfunction occurs in association with abnormal storage of electrolytes, including sodium, potassium, chloride and phosphate ions. These changes are due to hepatic injury, reduced albumin synthesis and impaired glucose and lipid metabolism, all of which are due to long-term oxidative stress. This stress is due to accumulation of ivermectin and inhibition of cytochrome P450 enzymes, followed by excessive formation of ROS and eventual exhaustion of antioxidant protection. This pattern is consistent with previous studies in mammals of oxidative and metabolic stress induced by ivermectin (Tawfeek et al., 2021; Salman et al., 2022; El-Shobokshy et al., 2023; Ali et al., 2025).

Conclusion

In summary, this study explains the adverse effects of ivermectin in rabbits. Ivermectin induces oxidative stress and mitochondrial dysfunction in liver tissue, leading to biochemical disorders that extend to renal dysfunction and electrolyte imbalance. These findings suggest that even therapeutic or prolonged exposure may induce interrelated hepatic and renal dysfunction.

Ethical considerations

This study was conducted in full compliance with the ethical guidelines approved by the Scientific Research Ethics Committee of the Faculty of Veterinary Medicine, University of Fallujah (Approval No. 6; 13/10/2025), https://doi.org/10.5281/zenodo.17832715. (Saud et al., 2025).