Effect of oral premedication with gabapentin and trazodone combination on the MAC of isoflurane in dogs

OBJECTIVE To determine the effect of the administration of oral gabapentin (20 mg/kg) and trazodone (8 mg/kg) on the MAC of isoflurane in dogs. METHODS 6 adult dogs (3 castrated males and 3 spayed females), aged 13.3 +/- 1.5 months and weighing 36.8 +/- 3.4 kg (mean +/- SD), were each anesthetized twice, separated by at least 7 days. Dogs were randomly assigned to receive gabapentin (20 mg/kg orally) and trazodone (8 mg/kg orally) followed by maintenance isoflurane or maintenance isoflurane alone. For their second event, dogs received the other treatment. The MAC was determined using an iterative bracketing technique with electric stimulation. Hemodynamic variables and vital parameters were assessed throughout the anesthetic episode. The effect of treatment on outcome variables was analyzed by use of a paired t test (P < .05). RESULTS The mean +/- SD MAC of isoflurane in dogs was significantly lower with gabapentin and trazodone premedication and isoflurane (0.625 +/- 0.18%) compared with isoflurane alone (0.95 +/- 0.14%). The mean MAC of isoflurane reduction was 0.33 +/- 0.04%. Heart rate was decreased but still within normal limits in premedicated dogs. Other hemodynamic variables did not differ significantly between treatments. CONCLUSIONS Oral administration of gabapentin (20 mg/kg) and trazodone (8 mg/kg) 2 hours before anesthesia maintained with isoflurane had a MAC-sparing effect with no significant effect on hemodynamic variables in dogs. CLINICAL RELEVANCE Oral premedication with gabapentin and trazodone could be administered before anesthesia to decrease MAC, thus limiting dose-dependent anesthetic risks.