Pharmakokinetik bei Neugeborenen und Säuglingen*

Abstract

Physiologic changes influence the pharmacokinetics of drugs relevant to anesthesia in neonates and infants. The neonatal phase is the phase of life with the most rapid and dramatic changes of organ-functions responsible for pharmacokinetics of most anesthetics. Changes in body composition and the content of plasma proteins influence volume of distribution, the drug distribution to different compartments and the amount of free fraction in plasma. Due to the immaturity of hepatic microsomal enzyme systems there is a decreased metabolism particular of agents which undergo low hepatic extraction like Diazepam, Morphine or some local anesthetics. In the first year of life capacity of the enzymatic systems increases and also clearance increases. Until puberty the clearance of some drugs is greater than the adult level. There are also pharmacodynamic changes like modified sensitivity to some drugs like volatile anesthetics or neuromuscular blocking agents. In summary neonates and infants are a highly heterogenous group with large interindividual differences. Therefore the dosage of anesthetic agents must be individualized to achieve optimal pharmacodynamic effects without toxicity in this age group.