title: The pharmacokinetics and metabolism of the anilide local anaesthetics in neonates. I. Lignocaine.
abstract: The pharmacokinetics and metabolism of lignocaine in premature neonates was studied after subcutaneous administration. The collection of serial urine together with a limited number of blood samples from neonates enabled simultaneous computer fitting of data to a pharmacokinetic model. The disposition kinetics of lignocaine in four neonates were compared with similar data reported for adults. Neonates had prolonged t1/2 (neonate mean: 3.16 h; adult mean: 1.80 h), and an increased total volume of distribution (neonate mean: 2.75 l/kg; adult mean: 1.11 l/kg) compared with adults. Total plasma clearance (Cltp) normalised on body weight showed no significant difference between neonates (mean: 0.610 l/h/kg) and adults (mean: 0.550 l/h/kg). The urinary excretion of lignocaine and several of its metabolites was studied in 8 neonates and 11 adults. Neonates were shown to excrete much more unchanged lignocaine (mean: 19.67%) compared with adults (mean: 4.27%) and the proportion of the dose excreted as 4-hydroxyxylidine is considerably reduced in neonates (neonate mean: 8.89%; adult mean: 63.78%). The use of the two pharmacokinetic parameters, t1/2 and Cltp, as indices of drug elimination ability are discussed.
mesh_terms: D000328:Adult; D000375:Aging; D001711:Biotransformation; D006801:Humans; D007231:Infant, Newborn; D007408:Intestinal Absorption; D007700:Kinetics; D008012:Lidocaine / Q000378:metabolism* / Q000652:urine; D008099:Liver / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D014018:Tissue Distribution
chemical_list: D008012:Lidocaine