Flumazenil has a dose-dependent effect on recovery from midazolam sedation in Rhode Island Red chickens (Gallus gallus domesticus)

Objective: To evaluate the pharmacodynamics of 3 doses of IM flumazenil following 5 mg/kg midazolam, IM, in Rhode Island Red chickens. Methods: Using a randomized, crossover design, hens received IM midazolam followed 25 minutes later by 1 of 4 treatments IM: 0.02, 0.05, or 0.1 mg/kg flumazenil or an equal volume of 0.9% sodium chloride (control). Serial assessment of heart and respiratory rates, sedation scores, and times to recumbency and standing were recorded from midazolam administration until recovery. Chickens not recovered by 3 hours after midazolam received 0.05 mg/kg flumazenil, IM (rescue). Categorical variables were analyzed with the Cochran Q test, whereas noncategorical variables were evaluated with a mixed-effects γ regression model. The Pearson correlation and intraclass correlation coefficient measured correlation between observers. Results: All six Rhode Island Red hens became recumbent following midazolam administration. Heart and respiratory rates remained within clinically acceptable limits. Median (range) time to recovery following 0.02, 0.05, or 0.1 mg/kg flumazenil or control was 153.9 (55.2 to 180.0), 137.3 (35.5 to 181.0), 70.7 (29.6 to 182.0), and 173.0 (151.0 to 181.0) minutes, respectively. This was statistically significant between groups. Rescue flumazenil was administered in 3 of 6, 3 of 6, 1 of 6, and 5 of 6 birds in 0.02, 0.05, and 0.1 mg/kg flumazenil or control, respectively. Conclusions: In chickens sedated with 5 mg/kg midazolam, IM, 0.1 mg/kg flumazenil provided the fastest time to recovery compared to lower doses (0.02 and 0.05 mg/kg) or control. Clinical Relevance: This study supports the use of 0.1 mg/kg flumazenil, IM, to expedite recovery in midazolam-sedated chickens.