[Pharmacokinetics of local anesthetics in children].

Anatomical and physiological differences between children and adults may induce changes in absorption, distribution and elimination of local anesthetics throughout life. Absorption is faster and the Cmax may be higher in children than in adults. In addition, the volume of distribution is larger, and the Cmax is lower and the terminal half-life is longer in children than in adults. The low level of albumin and alpha-1-acid-glycoprotein until 6 months of life, may result in an increase in free fraction of drugs, as it has been demonstrated for bupivacaine. In clinical practice, the decrease in protein binding in infants may lead to careful use before the age of 6 months. It seems preferable to use drugs with moderate protein binding and high hepatic extraction ratio such as lidocaine; the repeated injection of epidural bupivacaine should be careful used because of the longer terminal half-life; maximum dosage regimens are for lidocaine 10 mg.kg-1 and for bupivacaine 2.5 mg.kg-1.