Effects of intravenous administration of ascorbic acid (vitamin C) on oxidative status in healthy adult horses

Abstract Background Ascorbic acid (AA) is an antioxidant that might be beneficial for adjunctive treatment of sepsis in horses. The optimal dose and effects on oxidative status are unknown. Hypothesis Ascorbic acid administration will increase plasma AA concentrations and decrease determinants of reactive oxygen metabolites (dROM), basal and stimulant‐induced intraerythrocytic reactive oxygen species (ROS) concentrations, and stimulant‐induced neutrophil ROS production, and increase plasma antioxidant capacity (PAC) in a dose‐dependent manner. Animals Eight healthy horses. Methods Randomized placebo‐controlled crossover study. Each horse received 4 single‐dose IV treatments including AA at 25, 50, and 100 mg/kg and saline (placebo) with each treatment separated by ≥1 week. Blood was collected at baseline, 2 and 6 hours for assessment of plasma dROM and PAC via photometer, intraerythrocytic ROS by flow cytometry, and stimulant‐induced neutrophil ROS by a fluorometric assay. Plasma AA concentrations were measured by high‐performance liquid chromatography/electrochemical detection. Results Ascorbic acid at 100 mg/kg resulted in decreased dROM 2 hours after treatment (P = .03, 95% CI 5.51‐121.2, point estimate 63.3). There was no effect of AA on basal or stimulant‐induced intraerythrocytic ROS (P = .88, 95% CI −0.156 to 0.081, point estimate −0.037; P = .93, 95% CI −0.123 to 0.112, point estimate −0.006, respectively), basal or stimulant‐induced neutrophil ROS (P ≥ .12, 95% CI −644.9 to 56.2, point estimate −294.4), or PAC (P ≥ .64, 95% CI −1567 to 463.4, point estimate −552.0) at any dose or timepoint. Plasma AA concentrations increased in a dose‐dependent manner. Conclusions and Clinical Importance High‐dose administration of AA might provide antioxidant benefits in horses.