Medetomidine-vatinoxan-methadone and acepromazine-methadone: comparison of sedative and cardiovascular properties as a preanaesthetic medication in healthy dogs.

BACKGROUND

Medetomidine-vatinoxan is a relatively new medicinal product indicated for sedation of healthy dogs. Vatinoxan alleviates medetomidine-induced bradycardia and peripheral vasoconstriction in dogs, but when used as a preanaesthetic medication, it has been shown to cause more hypotension during general anaesthesia compared to medetomidine alone. Our aim was to compare medetomidine-vatinoxan to acepromazine when used as a preanaesthetic medication in a randomised, blinded, clinical study. Healthy client-owned dogs (n = 25) scheduled for elective ovariectomy were randomly assigned to receive 0.2 mg/kg intramuscular methadone combined with either 0.01 mg/kg medetomidine and 0.2 mg/kg vatinoxan (group MV, n = 13) or 0.02 mg/kg acepromazine (group A, n = 12). A sedation scale (SS, range 0-12) and visual analogue scale (VAS, range 0-100 mm) were applied to assess sedation every 5 min until one of the following endpoints was reached: the SS was ≥ 6 or30 min from treatment had passed. After this, general anaesthesia was induced with propofol and maintained with sevoflurane vaporised in oxygen. The need for cardiovascular interventions according to current guidelines was recorded. Statistical comparisons were performed with Student's t test, the Mann‒Whitney U test and Fisher's exact test. P-values < 0.05 were considered statistically significant.

RESULTS

The median (range) time to achieve an SS ≥ 6 was 5 (5-10) minutes in the MV group and 20 (10-25) minutes in the A group (P-value < 0.001). The number of dogs needing interventions for hypotension, bradycardia and/or bradyarrhytmias (7 in group MV, 8 in group A) did not significantly differ between the groups.

CONCLUSIONS

When used as a preanaesthetic medication in combination with methadone, medetomidine-vatinoxan causes faster onset of sedation, without statistically significant differences in cardiovascular interventions, compared to acepromazine.