Immobilisation and clinical effects of four drug combinations used to chemicallycapture white rhinoceros (Ceratotherium simum)

Authors

DOI:

https://doi.org/10.36303/JSAVA.722

Keywords:

cardiopulmonary, etorphine, azaperone, midazolam, medetomidine

Abstract

Etorphine is an ultra-potent opioid used to immobilise white rhinoceros (Ceratotherium simum) in the field, but it can also cause extensive metabolic and cardiorespiratory derangements. To potentially reduce the severity of these derangements, etorphine is combined with synergistic drugs including medetomidine (an alpha-2 adrenoreceptor agonist), midazolam (a benzodiazepine agonist), or azaperone (a butyrophenone drug). The potentiation effects of these synergistic drugs are believed to reduce induction times and excitement, induce muscle relaxation, and improve immobilisation quality and safety.

To test the benefits of these synergistic drugs, eight healthy, wild-caught boma-housed white rhinoceros (sub-adult males) were used in a repeated-measures randomised cross-over study. Each rhinoceros was immobilised with four treatments: etorphine only (control), etorphine + azaperone (azaperone), etorphine + medetomidine (medetomidine), and etorphine + midazolam (midazolam). Butorphanol was administered intravenously after 12 min of immobilisation in all treatments. First signs of drug effects, immobilisation induction times, immobilisation quality, tremor scores, rectal temperature, heart and respiratory rates, and peripheral arterial oxygen-haemoglobin saturation, were compared between and within treatments.

All four treatments effectively immobilised rhinoceros, however the addition of azaperone, medetomidine and midazolam were associated with significantly shorter induction times compared to the etorphine-only.

All treatments initially caused severe muscle tremors, hypopnea, hypoxaemia, and tachycardia (except for medetomidine). The administration of butorphanol partly corrected most of these derangements.

Our study shows that the synergistic drugs effectively speed up induction into immobilisation. However, they provide little other physiological or clinical benefit over etorphine-only. Butorphanol remains an important ancillary treatment when administering these drug combinations in rhinoceros.

Author Biographies

  • MM Ndunda, University of Pretoria

    Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, South Africa
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Center for Zoo and Wild Animal Health, Copenhagen Zoo, Denmark
    Kenya Wildlife Service, Department of Veterinary and Capture Services, Kenya

  • PE Buss, University of Pretoria

    Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, South Africa
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Veterinary Wildlife Services, South African National Parks, Kruger National Park, South Africa

  • RD Gleed, Cornell University

     Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, United States of America

  • AC Donaldson, University of Pretoria

    Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, South Africa
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, South Africa

  • M Leiberich, University of Pretoria

    Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, South Africa
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa

  • EH Hooijberg, University of Pretoria
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, South Africa
  • EP Snelling, University of Pretoria

    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, South Africa

  • JM Boesch, Cornell University

    Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, United States of America

  • LCR Meyer, University of Pretoria

    Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, South Africa
    Centre for Veterinary Wildlife Research, Faculty of Veterinary Science, University of Pretoria, South Africa
    Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, South Africa
    Animal Welfare Science and Bioethics Centre, School of Veterinary Science, Massey University, New Zealand

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Published

2026-03-26

Issue

Vol. 97 No. 1 (2026)

Section

Original Research

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Copyright (c) 2026 Author/s

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.