ELEVATED BRAIN CONCENTRATIONS OF 1,4-BENZODIAZEPINES IN FULMINANT HEPATIC-FAILURE

Background. Increased gamma-aminobutyric acid (GABA) neurotransmission has been implicated in the pathogenesis of hepatic encephalopathy. The mechanism by which GABA-ergic activity is increased in hepatic failure is unclear, but recent studies in animals with encephalopathy due to fulminant hepatic failure suggest that GABA-ergic neurotransmission may be increased by the presence of elevated concentrations of benzodiazepine agonists such as diazepam and N-desmethyldiazepam. Methods and Results. Samples of frontal cortex were obtained at autopsy from 11 patients with hepatic encephalopathy who died of acetaminophen-induced fulminant hepatic failure and 8 patients who died of cardiovascular disease or trauma. None of the 19 patients had received benzodiazepines while hospitalized. Chromatographic analyses of extracts of these samples revealed 4 to 19 peaks representing substances that inhibited the binding of a radiolabeled imidazobenzodiazepine ([H-3]flumazenil) to its receptors. Several of these peaks had retention times corresponding to those of known 1,4-benzodiazepines. Ultraviolet- and mass-spectroscopic analysis confirmed that two of these peaks represented diazepam and N-desmethyldiazepam. The patients who died of fulminant hepatic failure could be divided into two groups: six who had had significantly elevated brain concentrations (2-fold to 10-fold higher than normal) of substances inhibiting the binding of [H-3]flumazenil and five who had normal concentrations. Conclusions. Brain concentrations of substances inhibiting the binding of [H-3]flumazenil to its receptors are increased in some patients with hepatic encephalopathy due to fulminant hepatic failure. The origin of these substances is unknown, but these findings provide a rational basis for trials of benzodiazepine-receptor antagonists in the management of this disorder.