The effects of xylazine, detomidine, acepromazine and butorphanol on equine solid phase gastric emptying rate

• Published in: Equine veterinary journal Vol. 34; no. 5; p. 486
• Main Authors: Sutton, D G M, Preston, T, Christley, R M, Cohen, N D, Love, S, Roussel, A J
• Format: Journal Article
• Language: English
• Published: United States 01.07.2002
• Subjects: Acepromazine - pharmacology; Adrenergic alpha-Agonists - pharmacology; Analgesics - pharmacology; Animals; Breath Tests; Butorphanol - pharmacology; Caprylates - pharmacokinetics; Carbon Dioxide - analysis; Carbon Isotopes; Dose-Response Relationship, Drug; Gastric Emptying - drug effects; Gastric Emptying - physiology; Gastroparesis - veterinary; Horses; Hypnotics and Sedatives - pharmacology; Imidazoles - pharmacology; Linear Models; Xylazine - pharmacology
• ISSN: 0425-1644
• DOI: 10.2746/042516402776117818

The aim of this study was to measure the effects of specific commonly used sedative protocols on equine solid phase gastric emptying rate, using the 13C-octanoic acid breath test (13C-OABT). The gastric emptying of a standard 13C-labelled test meal was measured once weekly in 8 mature horses over two 4 week treatment periods. Each horse acted as its own control. In treatment Period 1, saline (2 ml i.v.), xylazine (0.5 mg/kg i.v.), detomidine (0.01 mg/kg i.v.) or detomidine/butorphanol combination (0.01/0.02 mg/kg i.v.) was administered in randomised order after ingestion of the test meal. During treatment Period 2, test meal consumption was followed by saline, xylazine (1.0 mg/kg i.v.), or detomidine (0.03 mg/kg i.v.) administration, or preceded by acepromazine (0.05 mg/kg i.m.) in randomised order. The 13C:12C ratio of sequential expiratory breath samples was determined by isotope ratio mass spectrometry, and used to measure the gastric half-emptying time, t 1/2, and duration of the lag phase, t lag, for each of the 64 tests. In treatment Period 1, detomidine/butorphanol prolonged both t 1/2 and t lag with respect to xylazine 0.5 mg/kg and the saline control (P < 0.05). In Period 2, detomidine 0.03 mg/kg delayed each parameter with respect to saline, acepromazine and xylazine 1.0 mg/kg (P < 0.001). Xylazine 1.0 mg/kg also lengthened t lag relative to the saline control (P = 0.0004), but did not cause a significant change in t 1/2. Comparison of treatment periods showed that the inhibitory effect of detomidine on gastric emptying rate was dose related (P<0.05). These findings may have clinical significance for case selection when these agents are used for purposes of sedation and/or analgesia.