Vitamin E is essential for neuromuscular function. Oral supplementation with natural (“RRR”) α-tocopherol has been the mainstay of therapy in horses with hypovitaminosis E. However, there is a subset of non-responsive horses. The objectives of this pilot trial were to evaluate the safety and efficacy of an injectable RRR-α-tocopherol preparation delivered subcutaneously. We hypothesized that RRR-α-tocopherol injection would increase serum and cerebrospinal fluid (CSF) α-tocopherol concentrations in healthy adult horses. Six mixed breed horses (3 mares and 3 geldings) and two untreated horses (1 mare and 1 gelding) were enrolled. In Phase I, horses were randomly assigned to receive RRR-α-tocopherol (5000 IU/450kg of 600 IU/mL) by subcutaneous (n=3) or oral (n=3) administration. Moderate tissue reaction following injection necessitated adjustment of the preparation through reduction of the RRR-α-tocopherol concentration to 500 IU/mL. Following an 8-week washout period, horses received the reciprocal treatment in Phase II with the new preparation at an equivalent dose. Alpha-tocopherol concentrations of serum and CSF collected over a 7d period were determined by HPLC. There was no difference in baseline serum (P=0.07) or CSF (P=0.20) concentrations and no residual effect noted, indicating appropriate washout. Serum (P <0.0001) and CSF (P=0.0.007) α-tocopherol concentrations increased significantly post-injection only when the 500 IU/mL product was administered, with serum concentrations peaking at 24h post-injection. This injectable formulation may therefore be useful in cases refractory to oral supplementation. However, caution is warranted due to the marked local tissue reaction observed in all horses.
Large Animal Internal Medicine Resident
University of California, Davis
Dr. Callum Donnelly obtained his veterinary degree from Charles Sturt University School of Veterinary Medicine in Australia. Upon graduation, he participated in a one-year rotating internship at the Goulburn Valley Equine Hospital in Victoria Australia. Dr. Donnelly then completed a residency in theriogenology at Cornell University College of Veterinary Medicine achieving board certification in 2016, before beginning his equine medicine residency at UC Davis in 2016.
Thursday, June 14
4:45 PM – 5:00 PM
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