Pharmacokinetics and pharmacodynamics of intravenous acetaminophen in neonates

Effective analgesia in neonates is still hampered owing to a lack of data on pharmacokinetics and pharmacodynamics of analgesics. In this article, the consecutive steps taken to document aspects of disposition (pharmacokinetics and metabolism) and safety (hepatic tolerance, hemodynamic stability and effects on body temperature) during exposure to intravenous acetaminophen in neonates are summarized. Based on these data, dosing suggestions were formulated. However, we have to be aware that such dosing suggestions are - at present - without any validated pharmacodynamic correlates since the applicability of a fixed acetaminophen target concentration (10 mg·l(-1)) in neonates of different subpopulations remains to be documented. In addition, the number of observations in extreme preterm neonates is limited. Finally, epidemiological data suggest a link between perinatal acetaminophen exposure and an increased risk to developing asthma. Consequently, well designed and appropriately powered pharmacodynamic studies in neonates are urgently required, with specific emphasis on extreme preterm neonates.