L-644,711, a novel anion transport inhibitor, increases isoflurane MAC in rats

The effect of the anion transport inhibitor L-644,711 on isoflurane MAC was determined in rats (n = 24). After baseline MAC determination, each rat received one of the following drug protocols: (a) control, vehicle only; (b) L-644,711IT, a 3-mg/kg intrathecal bolus of L-644,711 followed by an infusion at 1.5 mg.kg-1.h-1; or (c) L-644,711IV, a 6-mg/kg intravenous bolus of L-644,711 followed by an infusion at 3 mg.kg-1.h-1. MAC was again determined. The baseline isoflurane MAC was not different between groups (control, 1.52% +/- 0.15%; L-644,711IT, 1.51% +/- 0.24%; L-644,711IV, 1.54% +/- 0.13% [mean +/- SD]). After drug or vehicle administration, isoflurane MAC was larger for the L-644,711IT group (2.25% +/- 0.17%) versus the control (1.38% +/- 0.13%) and L-644,711IV (1.39% +/- 0.15%) groups (P less than 0.05). These data are consistent with the hypothesis that isoflurane anesthesia is influenced by anion channels and that blocking these channels may reduce the pharmacodynamic potency of isoflurane.