The formation of monoethylglycinexylidide (MEGX), a first order metabolite of lidocaine, is useful as a noninvasive index of hepatic function. We hypothesized that hepatic function is impaired in cystic fibrosis and could be assessed in these patients by MEGX formation. MEGX concentration was measured at 15 min following IV injection of 1 mg/kg (max 50 mg) lidocaine in 10 patients with cystic fibrosis (18 ± 9 yr., mean ± SD) and 17 controls of similar age, sex, and race. Serum bilirubin, alkaline phosphatase, and aminotransferases were normal in all patients. Indocyanine green (ICG, 0.5 mg/kg) was injected concomitantly and absorbance (805 nm) of serum was measured at 5, 10, 15, and 20 min to determine its volume of distribution(VD), serum half-life (t1/2) and hepatic blood flow (QH). The results are shown below as mean ± SE: Table Our results show that hepatic drug metabolism is decreased in patients with cystic fibrosis compared with controls (p<0.05). The differences in hepatic blood flow, volume of distribution, and half-life were not significant. We conclude that hepatic drug metabolism, as assessed by MEGX formation following lidocaine injection, is impaired in patients with cystic fibrosis. This impairment may have clinical implications when using hepatically metabolized medications in patients with cystic fibrosis. We speculate that MEGX formation may be useful as a noninvasive indicator of hepatic function in cystic fibrosis.

Table 1
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