The effects of intravenous gabapentin administration on the minimum alveolar concentration of isoflurane in cats

BACKGROUND: Gabapentin is a structural analog of ±-aminobutyric acid, one of the inhibitory neurotransmitters of the mammalian central nervous system. It is increasingly being used preemptively to control postoperative pain. Therefore, its interaction with inhaled anesthetics is of clinical interest. In this study, we examined the effects of gabapentin on the minimum alveolar concentration (MAC) of isoflurane in cats. We hypothesized that gabapentin would decrease the MAC of isoflurane in a dose-dependent manner. METHODS: Six cats were included in the study. Gabapentin was administered IV to achieve target plasma concentrations between 0 and 16 μg/mL and the MAC of isoflurane was determined at each gabapentin concentration. Gabapentin concentrations were quantitated by liquid chromatography-mass spectrometry analysis of extracted plasma samples. MAC values at the different gabapentin plasma concentrations were analyzed by a repeated-measures analysis of variance using the Huynh-Feldt correction for violation of the sphericity assumption. RESULTS: Actual gabapentin concentrations were 0 ± 0, 1.18 ± 0.23, 2.25 ± 0.23, 4.96 ± 1.19, 10.63 ± 1.37, and 19.69 ± 3.97 ±g/mL for the target concentrations of 0, 1, 2, 4, 8, and 16 μg/mL, respectively. The MAC of isoflurane in this study was 2.10% ± 0.13%, 2.10% ± 0.14%, 2.13% ± 0.12%, 2.06% ± 0.11%, 2.11% ± 0.15%, and 2.09% ± 0.25% at target plasma concentrations of 0, 1, 2, 4, 8, and 16 μ g/mL, respectively. CONCLUSIONS: We conclude that gabapentin did not have a detectable effect on the MAC of isoflurane in cats. (Anesth Analg 2010;111:633-7)