The effects of xylazine, detomidine, acepromazine and butorphanol on equine solid phase gastric emptying rate.
Authors: Sutton D G M, Preston T, Christley R M, Cohen N D, Love S, Roussel A J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Sedative Effects on Gastric Emptying in Horses Using 13C-octanoic acid breath testing, this 2002 study investigated how four commonly administered sedative and analgesic drugs affected solid-phase gastric emptying in eight horses tested repeatedly over two four-week periods. Detomidine showed clear dose-dependent inhibition of gastric motility, with the higher dose (0.03 mg/kg) significantly prolonging both the lag phase and gastric half-emptying time compared to saline, acepromazine and xylazine at 1.0 mg/kg (P<0.001), whilst the lower dose (0.01 mg/kg) combined with butorphanol also delayed emptying relative to xylazine 0.5 mg/kg and control (P<0.05). Xylazine at 1.0 mg/kg extended the lag phase but had minimal impact on overall emptying rate, and acepromazine appeared largely neutral. For practitioners selecting sedation protocols—particularly before gastric procedures, in colic cases, or in horses with compromised GI function—these findings suggest detomidine carries genuine risk of delayed gastric clearance in a dose-dependent manner, whereas xylazine may offer a safer alternative when gastric transit is a clinical concern.
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Practical Takeaways
- •When selecting sedative protocols for horses, clinicians should consider that detomidine—especially at higher doses—significantly delays gastric emptying and may increase colic risk in susceptible patients or those with gastric compromise
- •Xylazine at lower doses (0.5 mg/kg) appears safer for gastric function than detomidine or detomidine/butorphanol combinations, though higher doses may still prolong the lag phase
- •Case selection matters: avoid high-dose detomidine or detomidine/butorphanol in horses with known gastric dysfunction, recent feed intake, or colic risk factors
Key Findings
- •Detomidine/butorphanol combination significantly prolonged gastric half-emptying time (t1/2) and lag phase duration compared to xylazine 0.5 mg/kg and saline control (P < 0.05)
- •Detomidine 0.03 mg/kg delayed gastric emptying parameters compared to saline, acepromazine and xylazine 1.0 mg/kg (P < 0.001)
- •Detomidine's inhibitory effect on gastric emptying was dose-dependent, with higher doses causing greater delay (P < 0.05)
- •Xylazine 1.0 mg/kg lengthened lag phase but did not significantly change half-emptying time compared to saline control (P = 0.0004)