title: Plasma paracetamol concentrations and pharmacokinetics following rectal administration in neonates and young infants.
abstract: BACKGROUND
  Despite widespread use in children pharmacokinetic data about paracetamol are relatively scarce, not the least in the youngest age groups. This study aimed to describe plasma paracetamol concentrations and pharmacokinetics of a single rectal paracetamol dose in neonates and young infants.
  
  
  METHODS
  Perioperatively, 17 neonates and infants < or =160 days of age received one rectal paracetamol dose (mean 23.9 mg/kg (+/-4.2 mg/kg)). Blood samples were drawn at 60, 120, 180, 240, 300 and 360 min, according to the infants' weights. Plasma paracetamol concentrations were measured by a Colorometric Assay, Ectachem Clinical Chemistry Slides (Johnson & Johnson Clinical Diagsnostics).
  
  
  RESULTS
  The plasma paracetamol concentrations were mainly below the therapeutic (i.e. antipyretic) range of 66-132 micromol/l and did not exceed 160 micromol/l in any infant. The mean maximum plasma concentration (Cmax) was 72.4 micromol/l (+/-33.5 micromol/l) and the time to Cmax, i.e. the mean Tmax was 102.4 min (_+59.1 min). The mean "apparent" terminal half-life (n=10) was 243.6 min (+/-114.1 min).
  
  
  CONCLUSIONS
  The absorption of rectal paracetamol (mean dose 23.9 mg/kg, +/-4.2mg/kg) in young infants <160 days is variable and often prolonged and achieves mainly subtherapeutic plasma concentrations.
authors.affiliation: Directorate of Anaesthesia, The Royal Hospital for Sick Children, Glasgow, Scotland, United Kingdom.
authors.forename: T G
authors.initials: TG
authors.lastname: Hansen
authors.forename: K
authors.initials: K
authors.lastname: O'Brien
authors.forename: N S
authors.initials: NS
authors.lastname: Morton
authors.forename: S N
authors.initials: SN
authors.lastname: Rasmussen
mesh_terms: D000042:Absorption; D000082:Acetaminophen / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D000285:Administration, Rectal; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D000768:Anesthesia, General; D000772:Anesthesia, Local; D001835:Body Weight; D003124:Colorimetry; D005260:Female; D005500:Follow-Up Studies; D006207:Half-Life; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D013488:Suppositories
chemical_list: D018712:Analgesics, Non-Narcotic; D013488:Suppositories; D000082:Acetaminophen