2023 journal article

Pharmacokinetics and pharmacodynamics of intramuscular alfaxalone in central bearded dragons (Pogona vitticeps): effect of injection site


By: S. Shippy*, H. Allgood*, K. Messenger n, J. Hernandez*, B. Gatson, M. Bustamante*, A. Alexander*, J. Wellehan Jr, A. Johnson*

author keywords: alfaxalone; bearded dragon; injectable anes-thesia; pharmacokinetics; Pogona vitticeps; sedation
MeSH headings : Animals; Anesthetics / pharmacology; Cross-Over Studies; Injections, Intramuscular / veterinary; Prospective Studies
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: June 26, 2023

<h2>Abstract</h2><h3>Objective</h3> To evaluate the pharmacodynamic effects and pharmacokinetics of a single intramuscular (IM) injection of alfaxalone in central bearded dragons (<i>Pogona vitticeps</i>) when injected at a cranial <i>versus</i> a caudal site. <h3>Study design</h3> Prospective, masked, randomized crossover study. <h3>Animals</h3> A total of 13 healthy bearded dragons weighing 0.48 ± 0.1 kg. <h3>Methods</h3> Alfaxalone (10 mg kg<sup>–1</sup>) was administered IM to 13 bearded dragons in the triceps muscle (cranial treatment) or the quadriceps muscle (caudal treatment) separated by 4 weeks. Pharmacodynamic variables included movement score, muscle tone score and righting reflex. Blood was obtained from the caudal tail vein using a sparse sampling methodology. Plasma alfaxalone concentrations were determined using liquid chromatography–mass spectrometry, and pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. Differences in variables between injection sites were analyzed using a nonparametric Wilcoxon signed-rank test for paired data with significance set at <i>p</i> ≤ 0.05. <h3>Results</h3> Time to loss of righting reflex score was not different, median (interquartile range), between cranial and caudal treatments [8 (5–11) and 8 (4–12) minutes, respectively, <i>p</i> = 0.72]. Time to recovery of righting reflex was also not different between cranial and caudal treatments [80 (44–112) and 64 (56–104) minutes, respectively, <i>p</i> = 0.75]. Plasma alfaxalone concentrations were not significantly different between treatments. The population estimate (95% confidence intervals) for volume of distribution per fraction absorbed was 1.0 (0.79–1.20) L kg<sup>–1</sup>, clearance per fraction absorbed was 9.6 (7.6–11.6) mL minute<sup>–1</sup> kg<sup>–1</sup>, absorption rate constant was 2.3 (1.9–2.8) minute<sup>–1</sup> and elimination half-life was 71.9 (52.7–91.1) minutes. <h3>Conclusions and clinical relevance</h3> Regardless of the injection site, IM alfaxalone (10 mg kg<sup>–1</sup>) produced reliable chemical restraint in central bearded dragons, appropriate for nonpainful diagnostic procedures or anesthetic premedication.