F-19 NMR-STUDIES OF ENFLURANE ELIMINATION AND METABOLISM

The elimination and metabolism of enflurane, a fluorinated ether anaesthetic, was studied by F-19 NMR in vivo in both rat liver and brain as well as human body fluids. In the liver of thiobarbitone-anaesthetized rats the half-life for enflurane following exposure to 0. 15% (v/v) for 30 min was 76 min but this could be decreased to 39 min by pretreatment of the animals with isoniazid (0. 1% in the drinking water for 7 days), an agent known to enhance enflurane metabolism. In these animals the major organic metabolite difluoromethoxy difluoroacetate (DFMDFA) was also detected by F-19 NMR in vivo. This metabolite was detected along with fluoride ion in rat and human urine and plasma by high resolution F-19 NMR. Human urine also contained signals from a probable DFMDFA conjugate and unexpectedly from trifluoroacetate.