Resumen de 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

Teppei Kanda, Satoko Ishihara, Miina Oka, Kaori Sako, Yoko Sato, Noritaka Maeta, Katsutoshi Tamura, Kayo Furumoto, Toshinori Furukawa

• 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 Teppei Kanda DVM, PhD; Satoko Ishihara BSC; Miina Oka BSC; Kaori Sako BSC; Yoko Sato BSC; Noritaka Maeta DVM, PhD; Katsutoshi Tamura DVM, PhD; Kayo Furumoto PhD; Toshinori Furukawa DVM, PhD Laboratory of Veterinary Nursing and Medication, Department of Comparative Animal Science, College of Life Science, Kurashiki University of Science and the Arts, 2640 Tsurajima-cho Nishinoura, Kurashiki, Okayama 712-8505, Japan. (Kanda, Ishihara, Oka, Sako, Sato); Veterinary Teaching Hospital, Department of Comparative Animal Science, College of Life Science, Kurashiki University of Science and the Arts, 2640 Tsurajima-cho Nishinoura, Kurashiki, Okayama 712-8505, Japan. (Kanda, Maeta, Tamura, Furumoto, Furukawa) Address correspondence to Dr. Kanda (k-teppei@sci.kusa.ac.jp).

  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.

  ANIMALS 5 healthy purpose-bred male Beagles.

  PROCEDURES 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 AND CLINICAL RELEVANCE 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.