Effects of Medetomidine, Dexmedetomidine and their combination with Acepromazine on the intraocular pressure (IOP), tear secretion and pupil diameter in dogs

Background: A great number of sedatives and anaesthetics have been used to perform surgeries or routine ophthalmologic examinations in animals and sometimes the combination of these medicines has more suitable effects than each one alone. Objectives: This paper aims to explore the main effects of Medetomidine + Acepromazine, Dexmedetomidine + Acepromazine on intraocular pressure, tear secretion and pupil diameter. Methods: To accomplish the aforementioned aim, 32 adult dogs (aged one-to-three-years-old) were clinically examined. Dogs were divided into four groups consisting of group DA, Dexmedetomidine (5 mu g/kg) + Acepromazine (0.05 mg/kg); Group D, Dexmedetomidine (5 mu g/kg); Group M, Medetomidine (10 mu g/kg); Group MA, Medetomidine (10 mu g/kg) + Acepromazine (0.05 mg/kg). The ocular factors including tear production, pupil diameter and intraocular pressure of both right and left eyes were first measured and then recorded in each dog at time T-0 (-15 min). Afterwards, the drugs were administered intramuscularly, based on which the ocular factors were re-measured at T-1 (+5 min), T-2 (+15 min) and T-3 (+20 min). All four groups showed a reduction in intraocular pressure, which was significant in DA, D and M groups. Results: Furthermore, there was a fluctuation in the amount of tear secretion in DA and D groups (increase and then decrease), as well as a significant reduction in M and MA groups. Decreasing in pupil diameter also occurred in all four groups, but the reduction was significant only in DA and MA groups. Conclusion: According to the results obtained, as the changes caused by the systemic administration of the above drug compounds did not exceed the physiological range, it can be concluded that these combinations could be utilized as suitable sedatives or pre-anaesthetic compounds in the eye surgeries.