The role of oxidative biotransformation of halothane in the guinea pig model of halothane-associated hepatotoxicity

The role of the oxidative pathway of halothane biotransformation in mediating the hepatotoxicity of halothane in the guinea pig was examined by utilizing the deuterated form of halothane (d-halothane), which is resistant to oxidative metabolism. Male outbred Hartley guinea pigs were exposed to either 1% v/v halothane or d-halothane, FI(O₂) = 0.21, for 4 h. Significant reductions in both oxidative and overall halothane biotransformation were observed with the use of d-halothane as indicated by decreased plasma levels of trifluoroacetic acid and bromide ion, respectively, immediately following exposure. Plasma fluoride ion, indicative of the reductive metabolism of halothane, was significantly increased with the use of d-halothane. These changes in metabolism were accompanied by a reduced hepatotoxic response as indicated by significantly decreased plasma ALT levels 24-96 h following exposure and a significantly lesser incidence of centrilobular necrosis. Thus, the oxidative biotransformation of halothane is implicated as a mechanism of injury in guinea pigs.