Sedative effects and pharmacokinetics of detomidine when administered intravenously and intravaginally as a gel in alpacas

Abstract

ObjectivesTo evaluate the sedative effects and pharmacokinetics of detomidine gel administered intravaginally to alpacas in comparison with intravenously (IV) administered detomidine. Study designRandomized, crossover, blinded experiment. AnimalsA group of six healthy adult female Huacaya alpacas (70.3 ± 7.9 kg). MethodsAlpacas were studied on two occasions separated by ≥5 days. Treatments were IV detomidine hydrochloride (70 μg kg−1; treatment DET–IV) or detomidine gel (200 μg kg−1; treatment DET–VAG) administered intravaginally. Sedation and heart rate (HR) were evaluated at intervals for 240 minutes. Venous blood was collected at intervals for 360 minutes after treatment for analysis of detomidine, carboxydetomidine and hydroxydetomidine using liquid chromatography–tandem mass spectrometry. Measured variables were compared between treatments and over time using mixed model analysis. Data are presented as the mean ± standard error of the mean, and a p value of <0.05 was considered significant. ResultsOnset of sedation was faster in treatment DET–IV (1.6 ± 0.2 minutes) than in treatment DET–VAG (13.0 ± 2.5 minutes). Time to maximum sedation was shorter in treatment DET–IV (8.3 ± 1.3 minutes) than in treatment DET–VAG (25 ± 4 minutes). Duration of sedation was not different between treatments. There was a significant linear relationship between sedation score and plasma detomidine concentration. HR was less than baseline for 60 and 125 minutes for treatments DET–IV and DET–VAG, respectively. The maximal decrease in HR occurred at 15 minutes for both treatments. The mean maximum plasma concentration of detomidine, time to maximum concentration and bioavailability for treatment DET–VAG were 39.6 ng mL−1, 19.9 minutes and 20%, respectively. Conclusions and clinical relevanceDetomidine administration at the doses studied resulted in moderate sedation when administered IV or intravaginally to alpacas.