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Comparison of high (5%) and low (1%) concentrations of micellar microemulsion propofol formulations with a standard (1%) lipid emulsion in horses

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  • 1 Department of Surgical and Radiological Sciences and Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 2 Department of Surgical and Radiological Sciences and Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 3 Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 4 Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.
  • | 5 MEDDS (Micro Emulsion Drug Delivery Systems) Inc, Civic Center Dr, Rancho Cucamonga, CA 91730.
  • | 6 MEDDS (Micro Emulsion Drug Delivery Systems) Inc, Civic Center Dr, Rancho Cucamonga, CA 91730.

Abstract

Objective—To compare anesthesia-related events associated with IV administration of 2 novel micellar microemulsion preparations (1% and 5%) and a commercially available formulation (1%) of propofol in horses.

Animals—9 healthy horses.

Procedures—On 3 occasions, each horse was anesthetized with 1 of the 3 propofol formulations (1% or 5% microemulsion or 1% commercial preparation). All horses received xylazine (1 mg/kg, IV), and anesthesia was induced with propofol (2 mg/kg, IV). Induction and recovery events were quantitatively and qualitatively assessed. Venous blood samples were obtained before and at intervals following anesthesia for quantification of clinicopathologic variables.

Results—Compared with the commercial formulation, the quality of anesthesia induction in horses was slightly better with the micellar microemulsion formulas. In contrast, recovery characteristics were qualitatively and quantitatively indistinguishable among treatment groups (eg, time to stand after anesthesia was 34.3 ± 7.3 minutes, 34.1 ± 8.8 minutes, and 39.0 ± 7.6 minutes in horses treated with the commercial formulation, 1% microemulsion, and 5% microemulsion, respectively). During recovery from anesthesia, all horses stood on the first attempt and walked within 5 minutes of standing. No clinically relevant changes in hematologic and serum biochemical analytes were detected during a 3-day period following anesthesia.

Conclusions and Clinical Relevance—Results suggest that the micellar microemulsion preparation of propofol (1% or 5%) has similar anesthetic effects in horses, compared with the commercially available lipid propofol formulation. Additionally, the micellar microemulsion preparation is anticipated to have comparatively low production costs and can be manufactured in various concentrations.

Contributor Notes

Partial financial support and supplies of propofol microemulsions were provided by MEDDS Incorporated.

Presented as a poster abstract at the Fall Meeting of the Association of Veterinary Anaesthetists, Vienna, Austria, September 2004.

The authors thank Don Hermes, Chris Scarlett, and Doug West for technical assistance.

Address correspondence to Dr. Boscan.