Extrahepatic production of the lignocaine metabolite monoethylglycinexylidide (MEGX).

The extrahepatic production of monoethylglycinexylidide (MEGX) from lignocaine was measured in a 20-year-old female rendered anhepatic while awaiting liver transplantation 4 days after a paracetamol overdose. Following hepatectomy and during continuous arteriovenous dialysis, cardiac stability and control over rising intracranial pressure was restored. Lignocaine (1 mg kg body weight-1 intravenously over 2 min) reached a subtherapeutic peak serum concentration of 0.89 mg l-1 and was rapidly and exponentially cleared, reaching the lower limit of detection after 5 h (cf. around 2 h in normal subjects). There was significant production of MEGX at extrahepatic sites with serum concentrations rising from undetectable levels to 15 micrograms l-1 at 15 min and to a peak of 30 micrograms l-1 at 2 h and falling thereafter. MEGX concentrations were similar in arterial, venous, and pulmonary arterial blood, suggesting minimal MEGX production in the heart, lungs or skeletal muscle. Extrahepatic production of MEGX may contribute to total MEGX formation and should be considered when interpreting test results.