Pharmacokinetics of lignocaine in children following caudal anaesthesia.

The time course of the plasma lignocaine concentration, following caudal anaesthesia, was studied in 11 healthy children (3.5-9 yr). Plasma lignocaine concentrations were measured for up to 6 h after administration (5 mg kg-1). Peak plasma concentration was 2.05 +/- 0.08 micrograms ml-1 and occurred at 28.2 +/- 2.9 min after administration. Pharmacokinetic parameters determined from a two-compartmental model were similar to those observed after the i.v. or extradural administration of lignocaine in adults, except for a longer half-life of elimination (155 +/- 32 min). Since the total body clearance of lignocaine was similar in children (15.4 +/- 1.2 ml min-1 kg-1) to that in adults, the longer half-life of elimination was attributed to a larger volume of distribution in the children (3.05 +/- 0.40 litre kg-1).