Effects of methoxyflurane anesthesia on the pharmacokinetics of 125I-IAZA in Sprague-Dawley rats

Effects of methoxyflurane anesthesia on the pharmacokinetics of intravenous 125I-IAZA in rats are reported. No significant differences in t(1/2alpha), t(1/2beta), V(SS), and ClTB for total radioactivity (125I-IAZA and metabolites) were observed between the anesthetized (Group 1, n = 4) and nonanesthetized (Group 2, n = 3) animals. For 125I-IAZA, ClTB increased from 646 +/- 52 mL/h/kg to 2250 +/- 351 mL/h/kg and t(1/2beta) decreased from 97.7 +/- 17.5 min to 35.6 +/- 5.4 min, for Groups 1 and 2, respectively. There were no differences in V(SS) or t(1/2alpha) between the two groups. These findings support literature reports of anesthetic effects on xenobiotic pharmacokinetics, and indicate a need for caution in the evaluation of preclinical imaging studies in which animals are immobilized with anesthetics.