Comparison of the effects of intranasal and intramuscular midazolam–butorphanol–ketamine on intraocular pressure, tear production and sedation in New Zealand White rabbits

Abstract

ObjectiveTo compare the effects of intranasal (IN) and intramuscular (IM) midazolam–butorphanol–ketamine on intraocular pressure (IOP), tear production (TP) and sedation in rabbits. Study designProspective, randomized, crossover experimental study. AnimalsFourteen male New Zealand White rabbits, aged 1–2 years, body mass 3.1 ± 0.8 kg (mean ± standard deviation). MethodsRabbits were administered midazolam (1 mg kg–1), butorphanol (1.5 mg kg–1) and ketamine (5 mg kg–1) via IN and IM routes. IOP, TP and sedation scores were assessed at 0 (before drug administration), 5, 15, 30, 45 and 60 minutes after drug administration. Heart rate (HR), respiratory rate (fR), rectal temperature (RT), noninvasive mean arterial blood pressure (MAP) and peripheral hemoglobin oxygen saturation (SpO2) were simultaneously recorded until 45 minutes after drug administration. The onset and duration of sedation and sedation scores were recorded. ResultsDrug delivery route had no significant impact on mean IOP (p = 0.271) or TP (p = 0.062), and there were no significant changes over time for IOP (p = 0.711) or TP (p = 0.372). Similarly, delivery route had no significant impact on HR (p = 0.747), fR (p = 0.872), RT (p = 0.379), MAP (p = 0.217) and SpO2 (p = 0.254). Sedation onset was faster with IN (3.0 ± 1.0 minutes) than with IM administration (4.9 ± 0.7 minutes) (p = 0.011), but sedation duration was significantly longer with IM (52.6 ± 7.2 minutes) than with IN delivery (30.7 ± 6.8 minutes) (p = 0.004). There was no significant difference in sedation scores between the two delivery routes at any of the recorded time points. Conclusions and clinical relevanceThe combination of midazolam–butorphanol–ketamine had minimal impact on physiological and ocular variables regardless of the route of administration, whereas IN drug administration led to a shorter onset and duration of action than IM administration.