Limit opioid use and monitor closely when used.

       Educate clients regarding adverse effects in horses.

       Seizures.

       Hyperthermia.

       Prognosis for recovery is good if respiratory and cardiovascular functions are maintained.

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      2 Boscan P, Van Hoogmoed LM, Pypendop BH, et al. Pharmacokinetics of the opioid antagonist N‐methylnaltrexone and its effects on gastrointestinal tract function in horses treated or not treated with morphine. Am J Vet Res. 2006; 67:998–1004

      3 Combie JD, Nugent TE, Tobin T, Pharmacokinetics and protein binding of morphine in horses. Am J Vet Res 1983; 44(5): 870–874.

      4 Gupta GC. Veterinary Toxicology, 2nd edn. San Diego: Elsevier, 2012.

      5 Matthews NS, Carroll GL, Review of equine analgesics and pain management. AAEP Proc 2007; 53:240–244.

      6 Reed SM, Bayly WM, Sellon DC, ed. Equine Internal Medicine, 4th edn. St Louis: Elsevier., 2018.

      7 Roger T, Bardon T, Ruckebusch Y. Colonic motor responses in the pony: relevance of colonic stimulation by opiate antagonists. Am J Vet Res 1985; 46:31–35.

      8 Van Hoogmoed LM, Boscan PL. In vitro evaluation of the effect of the opioid antagonist N‐methylnaltrexone on motility of the equine jejunum and pelvic flexure. Equine Vet J 2005; 37:325–328.