Differential effect of chronic renal failure on the pharmacokinetics of lidocaine in patients receiving and not receiving hemodialysis.

BACKGROUND AND OBJECTIVES

The effect of chronic renal failure (CRF) on the pharmacokinetics of lidocaine, a drug cleared almost exclusively by hepatic metabolism, has thus far only been evaluated in patients undergoing regular hemodialysis. This study had 2 objectives: (1) to investigate the effect of CRF on the pharmacokinetics of lidocaine in both patients undergoing hemodialysis and patients not undergoing hemodialysis and (2) to test the effects of plasma from the patients examined and of lidocaine metabolites possibly accumulated in vivo on lidocaine biotransformation in vitro.

METHODS

In a clinical investigation we studied the kinetics of lidocaine and its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), after intravenous injection of 1 mg/kg lidocaine in 15 healthy volunteers (creatinine clearance [CL(cr)] >80 mL/min x 1.73 m(-2)), 10 subjects with moderate renal insufficiency (CL(cr) between 30 and 60 mL/min x 1.73 m(-2)), 10 subjects with severe renal insufficiency (CL(cr) <30 mL/min x 1.73 m(-2)), and 10 functionally anephric patients undergoing long-term hemodialysis. In experiments in vitro we determined the effects of plasma and GX on the formation rate of the primary lidocaine metabolite, MEGX, by use of human liver microsomes.

RESULTS

In patients not undergoing hemodialysis, lidocaine kinetic parameters were altered in proportion to the degree of renal function impairment, but only in patients with severe renal insufficiency were differences statistically significant: clearance was about half that of control subjects (mean +/- SD, 6.01 +/- 2.54 mL/min x kg versus 11.87 +/- 2.97 mL/min x kg; P < .001), and half-life was approximately doubled (4.55 +/- 1.71 hours versus 2.24 +/- 0.55 hours, P < .001). No such alterations were observed in patients undergoing regular hemodialysis, whose values were similar to those of the control group. The steady-state volume of distribution and MEGX levels were independent of renal function, whereas GX levels were more than double those of control subjects (P < .05) in all CRF groups. No inhibitory effect of plasma was observed, for any of the subjects examined, on lidocaine biotransformation in vitro. GX was found to be a competitive inhibitor, but its apparent inhibition constant value (52 +/- 6 micromol/L) was 2 orders of magnitude higher than its concentrations in vivo.

CONCLUSIONS

Our in vivo findings have both clinical and methodologic implications: (1) Lidocaine dose adjustment may be required in patients with severe renal insufficiency who are not receiving hemodialysis. (2) Results of studies evaluating the effect of CRF on metabolic drug disposition are not of general validity, unless both patients undergoing hemodialysis and patients not undergoing hemodialysis have been examined. Our in vitro observations exclude that impairment of lidocaine disposition is the result of direct inhibition of metabolizing enzymes by accumulated metabolites or uremic toxins. Alternative mechanisms, suggested by the results of recent in vitro studies, are discussed.