Effects of alpha2-adrenergic receptor agonists on urine production in horses deprived of food and water.
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.


METHODS
6 horses.


METHODS
Feed and water were withheld for 24 hours followed by i.v. administration of saline (0.9% NaCI) 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
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 alpha2-adrenergic receptor agonist. Dehydration in horses may be exacerbated by concurrent administration of alpha2-adrenergic receptor agonists.
Nuñez
Enrique
E
Department of Medicine and Surgery in Equines, School of Veterinary Medicine, National Autonmous University of México, Villa Obregón, México City, México.
Steffey
Eugene P
EP
Ocampo
Luis
L
Rodriguez
Alejandro
A
Garcia
Alma A
AA
D000322:Adrenergic Agonists / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005508:Food Deprivation / Q000502:physiology; D006029:Glycosuria / Q000652:urine; D006736:Horses / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D011188:Potassium / Q000097:blood / Q000652:urine; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D012964:Sodium / Q000097:blood / Q000652:urine; D014554:Urination / Q000187:drug effects*; D014868:Water Deprivation / Q000502:physiology; D014991:Xylazine / Q000494:pharmacology
D000322:Adrenergic Agonists; D007093:Imidazoles; D018341:Receptors, Adrenergic, alpha-2; D014991:Xylazine; C041255:detomidine; D012964:Sodium; D011188:Potassium