Effects of intraperitoneal administration of gabapentin on the minimum alveolar concentration of isoflurane in adult male rats

Gabapentin has been used to treat a variety of conditions in both human and veterinary medicine, including seizures, neuropathies and chronic pain. However, little information is known about the effects of gabapentin on the minimum alveolar concentration (MAC) of volatile anaesthetics. In this study, we investigated the effect of intraperitoneal administration of gabapentin on isoflurane MAC in adult male rats and hypothesized that gabapentin would decrease MAC in a dose-dependent manner. Using a standard MAC study protocol, we compared five treatment groups (G) receiving 0 (G(0)), 30 (G(30)), 100 (G(100)), 300 (G(300)) and 1000 (G(1000)) mg/kg gabapentin intraperitoneally and compared post-drug MAC values among groups and with corresponding baseline MAC values determined in each group prior to drug testing. The average baseline isoflurane MAC value was 1.45 +/- 0.17%, which did not differ significantly between groups (1.47 +/- 0.23% [G(30)], 1.46 +/- 0.23% [G(100)], 1.48 +/- 0.18% [G(300)] and 1.42 +/- 0.2% [G(1000)]). In the G(300) and G(1000) groups, the isoflurane MAC value decreased significantly by 19% and 18%, respectively, from corresponding baseline values (P < 0.05, when compared with G(0)). Linear regression analysis revealed a negative correlation between blood gabapentin concentration and percent change in MAC (R-2 = 0.43; P < 0.05) but not dose. In conclusion, high-dose intraperitoneal gabapentin decreased isoflurane MAC. However, the effect was small and not dose-dependent, and is unlikely to be clinically significant.