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Objective—To quantitate the dose- and time-related effects of IV administration of xylazine and detomidine on urine characteristics in horses deprived of feed and water.

Animals—6 horses.

Procedure—Feed and water were withheld for 24 hours followed by IV administration of saline (0.9% NaCl) solution, xylazine (0.5 or 1.0 mg/kg), or detomidine (0.03 mg/kg). Horses were treated 4 times, each time with a different protocol. Following treatment, urine and blood samples were obtained at 15, 30, 60, 120, and 180 minutes. Blood samples were analyzed for PCV and serum concentrations of total plasma solids, sodium, and potassium. Urine samples were analyzed for pH and concentrations of glucose, proteins, sodium, and potassium.

Results—Baseline (before treatment) urine flow was 0.30 ± 0.03 mL/kg/h and did not significantly change after treatment with saline solution and low-dose xylazine but transiently increased by 1 hour after treatment with high-dose xylazine or detomidine. Total urine output at 2 hours following treatment was 312 ± 101 mL versus 4,845 ± 272 mL for saline solution and detomidine, respectively. Absolute values of urine concentrations of sodium and potassium also variably increased following xylazine and detomidine administration.

Conclusions and Clinical Relevance—Xylazine and detomidine administration in horses deprived of feed and water causes transient increases in urine volume and loss of sodium and potassium. Increase in urine flow is directly related to dose and type of α2-adrenergic receptor agonist. Dehydration in horses may be exacerbated by concurrent administration of α2-adrenergic receptor agonists. (Am J Vet Res 2004;65:1342–1346)

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in American Journal of Veterinary Research



To examine changes occurring in normal pelvic suspensory ligaments (SLs) of horses after denervating these ligaments and to investigate the effect chronic inflammation might have on these changes.


10 horses.


The SL of 1 randomly selected pelvic limb of each of 5 horses was injected with collagenase to induce desmitis, and 42 days later, the proximal aspect of both pelvic SLs were denervated. The SLs were harvested 120 days after being denervated, and the morphological and histological characteristics of each collagenase-injected, denervated SL were compared with those of the contralateral, non-injected, denervated SL. All denervated SLs were compared with non-denervated pelvic SLs harvested from 5 horses similar in weight and age.


The mean width and the cross-sectional area of the musculature of all denervated SLs were significantly less than that of the non-denervated ligaments. The mean thickness of collagenase-injected denervated ligaments, but not that of the non-injected denervated ligaments, was significantly less than that of the non-denervated ligaments. Histological abnormalities typical of neurogenic muscular atrophy were observed in all denervated ligaments.


Loss of motor neuronal input to the proximal aspect of the SL of the pelvic limb of horses causes neurogenic atrophy of the musculature in that portion of the ligament. Denervating a SL of a pelvic limb may weaken the ligament, increasing its risk of injury. Chronic inflammation of the SL before neurectomy may exacerbate atrophy of the musculature after neurectomy.

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in American Journal of Veterinary Research