title: Temporal effects of intramuscular administration of medetomidine hydrochloride or xylazine hydrochloride to healthy dogs on tear flow measured by use of a Schirmer tear test I.
abstract: OBJECTIVE
  To determine the temporal effects on tear flow measurements obtained by use of a Schirmer tear test (STT) I after IM administration of various doses of medetomidine or xylazine to healthy dogs.
  
  
  METHODS
  5 healthy purpose-bred male Beagles.
  
  
  METHODS
  Each dog received IM injections of 2.0 mL of physiologic saline (0.9% NaCl) solution (control treatment); 0.1% medetomidine hydrochloride (5, 10, 20, and 40 μg/kg), and 2.0% xylazine hydrochloride (0.5, 1.0, 2.0, and 4.0 mg/kg). Treatments were injected into the semimembranosus muscles; there was at least a 1-week interval between successive injections. Order of treatments was determined via a randomized Latin square crossover design. The STT I was performed on both eyes before (baseline) and 0.25, 0.50, 0.75, 1, 2, 3, 4, 5, 6, 7, 8, and 24 hours after each injection.
  
  
  RESULTS
  STT I values decreased significantly within 45 minutes after injection of medetomidine or xylazine, which was followed by gradual recovery. The lowest mean STT I value was < 10 mm/min for all sedation treatments, except when dogs received 5 μg of medetomidine/kg. Linear regression of the area under the curve for the 8 hours after administration yielded significant effects for all sedation treatments.
  
  
  CONCLUSIONS
  IM administration of medetomidine or xylazine to dogs reduced tear flow in a dose-related manner. Artificial tear solution or ophthalmic ointment should be used to protect the ocular surface when these drugs are administered to dogs.
authors.forename: Teppei
authors.initials: T
authors.lastname: Kanda
authors.forename: Satoko
authors.initials: S
authors.lastname: Ishihara
authors.forename: Miina
authors.initials: M
authors.lastname: Oka
authors.forename: Kaori
authors.initials: K
authors.lastname: Sako
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sato
authors.forename: Noritaka
authors.initials: N
authors.lastname: Maeta
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Tamura
authors.forename: Kayo
authors.initials: K
authors.lastname: Furumoto
authors.forename: Toshinori
authors.initials: T
authors.lastname: Furukawa
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D007273:Injections, Intramuscular / Q000662:veterinary; D008297:Male; D020926:Medetomidine / Q000008:administration & dosage / Q000494:pharmacology*; D013666:Tears / Q000187:drug effects*; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D014991:Xylazine; D020926:Medetomidine