Effect of Xylazine HCl and/or Ketamine HCl on the Tear Production in Clinically Healthy Dogs

Objective: The effect of commonly used sedative and anesthetic drugs (xylazine and ketamine HCl) on tear production rate was evaluated in dogs using Schirmer tear test-I (STT I). Materials and Methods: Tear production using Schirmer tear strips were measured in healthy dogs before and after intramuscular injection of 1mg/kg of xylazine HCl (X; n = 4), 5 mg/kg of Ketamine HCl (K; n = 4), and combination of xylazine (1mg/kg) and ketamine (5 mg/ kg) (XK; n = 4). The tear production was recorded at times 0, 10, 20 and 30 minutes after injection of drugs. Results: Tear production rate significantly decreased (P< 0.05) at 10, 20 and 30 minutes from xylazine injection. It significantly increased (P< 0.05) at 30 minutes elapsed after ketamine injection. In the third group (XK), there was a significant decrease in tear production until 20 minutes after the injection of drugs. The effect of ketamine appeared clearly after 30 minutes to return the STT I values mostly to the pre-treatment values. Conclusion: The study recommends the use of a sterile ocular lubricant or tears replacement as a corneal protectant in dogs sedated or anesthetized using xylazine or a combination of xylazine-ketamine respectively.