The research team, based at Selcuk University’s Faculty of Veterinary Medicine, worked with ten male Akkaraman sheep aged eight to twelve months and weighing between 45 and 55 kilograms. The animals were housed under identical conditions with food and water available ad libitum, and the experimental protocol received approval from the university’s ethics committee. Each sheep received mefepronic acid by intramuscular injection into the gluteal muscles at 10 milligrams per kilogram once daily for three days, matching the dose and duration commonly used off-label in the field. Blood samples were drawn before the first injection and again at 24, 48 and 72 hours, allowing the researchers to track each animal against its own baseline in a repeated-measures, self-controlled design.

The analytical strategy was deliberately broad. Using sheep-specific ELISA kits and an autoanalyzer, the team measured a panel of oxidative stress markers: 8-hydroxy-2-deoxyguanosine, the most widely used biomarker of DNA damage from oxidative stress; malondialdehyde, a cytotoxic and mutagenic end product of lipid peroxidation; and the antioxidant enzymes superoxide dismutase, glutathione peroxidase and catalase. Cardiac injury was assessed through creatine kinase-MB isoenzyme and troponin I, while liver and bile duct status was tracked via alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase and total bilirubin. Kidney function was gauged by blood urea nitrogen and creatinine, and lipid metabolism by cholesterol, triglycerides, high-density lipoprotein and low-density lipoprotein. Data were tested for normality with the Shapiro-Wilk test, log-transformed where necessary, and analysed with repeated measures ANOVA and Bonferroni post-hoc comparisons.

Clinically, the drug was uneventful. None of the sheep developed fever, shivering, salivation or any other observable adverse reaction over the three-day monitoring window. Beneath that calm surface, however, the serum chemistry told a more nuanced story. Levels of 8-OHdG rose significantly at 24 hours, climbing from a baseline of roughly 4.86 nanograms per millilitre to 7.37, before drifting back toward starting values by 72 hours. Catalase activity, by contrast, declined significantly by the end of the study, falling from 4.22 to 3.02 nanograms per millilitre. Malondialdehyde, superoxide dismutase and glutathione peroxidase all fluctuated without reaching statistical significance, and the authors note that the isolated 8-OHdG spike, unaccompanied by changes in the other oxidative markers, cannot be directly interpreted as genuine DNA damage.

The cardiac findings followed a similar pattern of transient change without clear pathology. Creatine kinase-MB isoenzyme levels jumped significantly at 24 hours, from 0.62 to 1.01 nanograms per millilitre, then returned to near-baseline values. Troponin I, the more cardiospecific biomarker that has largely displaced CK-MB in clinical practice because of its superior specificity for heart muscle, showed no significant change at any time point. The authors place this result in context by explaining that CK-MB is a sensitive but nonspecific marker: it is produced predominantly in cardiac muscle but also in small amounts in the uterus, small intestine, diaphragm, tongue and prostate, and its rapid clearance from circulating blood has historically limited its diagnostic value. Given that troponin I remained stable, the team concluded that no clinically significant myocardial damage occurred during the short observation period.

Kidney and lipid parameters produced the study’s most intriguing metabolic signals. Blood urea nitrogen fell significantly by 72 hours, from 11.31 to 9.01 milligrams per decilitre, though the decline stayed within published reference ranges for sheep and serum creatinine, the more reliable indicator of glomerular filtration rate, remained unchanged throughout. High-density lipoprotein dropped significantly by 72 hours and low-density lipoprotein fell significantly at both 24 and 72 hours, the latter sliding from 27.50 to 19.00 milligrams per decilitre. Cholesterol and triglycerides also trended downward without reaching significance. The authors suggest these lipid shifts are consistent with the drug’s known metabolic activity and may even underpin its reported benefits in fatty liver syndrome, where reducing circulating lipid load could ease the burden on an already compromised liver.

Liver markers were similarly unremarkable. Alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase and total bilirubin all showed nonsignificant decreases over the study period, a direction of change that fits comfortably with the drug’s intended choleretic action rather than suggesting hepatocellular injury. This aligns with earlier reports in other species: mefepronic acid given to dairy cows before and after calving had no adverse effect on serum lipid parameters and appeared to improve postpartum liver function, and the compound has been used as supportive therapy in dogs with hepatopathy. Rat studies have also reported a limited protective effect against hepatic steatosis, and off-label use in sheep has been credited with helping correct the severe metabolic liver dysfunction associated with liver fluke infection when combined with triclabendazole and levamisole.

The study’s design choices carry both strengths and constraints that shape how the results should be read. The self-controlled, repeated-measures framework meant each animal served as its own reference, which the authors argue reduced the noise introduced by inter-individual biological variation and allowed clean tracking of time-dependent changes after dosing. But the absence of a separate control group means drug-related effects cannot be fully disentangled from spontaneous or time-dependent physiological drift. The sample of ten healthy male sheep, monitored for only 72 hours, further limits generalisation. The authors are explicit that these are preliminary data, and they flag particular caution for animals with pre-existing heart disease or other risk factors, where the transient CK-MB elevation and catalase decline could behave differently.

Species-specific idiosyncrasies in drug safety provide a compelling rationale for the work. Tilmicosin, a macrolide antibiotic considered safe in cattle, has been reported to cause mortality in goats. Ivermectin, a mainstay antiparasitic that is generally well tolerated in dogs, produces toxicity and death in Collies carrying the MDR1 mutation. Against that backdrop, assuming that a drug proven safe in five target species will behave identically in a sixth is clearly untenable. The oxidative stress angle added further urgency: prior work in dairy cattle suggested mefepronic acid can reduce lipid peroxidation in hepatocytes, and researchers have proposed that the drug, alone or with ammonium molybdate, might help in copper poisoning cases in sheep, making it important to know whether the compound itself provokes oxidative damage at therapeutic doses.

The overall verdict is one of conditional reassurance. In healthy sheep at the standard 10 milligrams per kilogram intramuscular dose for three days, mefepronic acid caused no clinical adverse effects, no clinically significant disturbance of liver or kidney function, and no evidence of myocardial injury by the most specific available biomarker. The transient 8-OHdG rise, catalase fall and CK-MB bump are best interpreted as subclinical, self-resolving fluctuations rather than signs of organ damage, though the authors caution that such effects could prove more pronounced in sick, pregnant or otherwise compromised animals. They call for future studies in different breeds and in diseased or pregnant sheep to establish whether the drug’s growing off-label repertoire in ovine medicine, from fertility support to metabolic disease, can rest on firmer safety ground. For now, the message to practitioners is measured: the drug appears tolerable in healthy ewes and rams, but risk groups deserve closer monitoring.

Subject of Research: Safety and biochemical effects of extra-label mefepronic acid administration in sheep

Article Title: Safety Assessment of Mefepronic Acid in Sheep

Article References: Canbar, R., Parlak, T. M., Uslu, M., & Yazar, E. (2026). Safety Assessment of Mefepronic Acid in Sheep. Veterinary Medicine and Science, 12(5), Article e71236. https://doi.org/10.1002/vms3.71236

Image Credits: AI Generated

DOI: 10.1002/vms3.71236

Keywords: mefepronic acid, sheep, veterinary pharmacology, oxidative stress, choleretic, cardiac biomarkers, CK-MB, troponin I, liver function, kidney function, lipid metabolism, drug safety