title: A bodyweight-dependent allometric exponent for scaling clearance across the human life-span.
abstract: OBJECTIVE
  To explore different allometric equations for scaling clearance across the human life-span using propofol as a model drug.
  
  
  METHODS
  Data from seven previously published propofol studies ((pre)term neonates, infants, toddlers, children, adolescents and adults) were analysed using NONMEM VI. To scale clearance, a bodyweight-based exponential equation with four different structures for the exponent was used: (I) 3/4 allometric scaling model; (II) mixture model; (III) bodyweight-cut-point separated model; (IV) bodyweight-dependent exponent model.
  
  
  RESULTS
  Model I adequately described clearance in adults and older children, but overestimated clearance of neonates and underestimated clearance of infants. Use of two different exponents in Model II and Model III showed significantly improved performance, but yielded ambiguities on the boundaries of the two subpopulations. This discontinuity was overcome in Model IV, in which the exponent changed sigmoidally from 1.35 at a hypothetical bodyweight of 0 kg to a value of 0.56 from 10 kg onwards, thereby describing clearance of all individuals best.
  
  
  CONCLUSIONS
  A model was developed for scaling clearance over the entire human life-span with a single continuous equation, in which the exponent of the bodyweight-based exponential equation varied with bodyweight.
authors.affiliation: Division of Pharmacology, LACDR, Leiden University, Leiden, the Netherlands.
authors.forename: Chenguang
authors.initials: C
authors.lastname: Wang
authors.forename: Mariska Y M
authors.initials: MY
authors.lastname: Peeters
authors.forename: Karel
authors.initials: K
authors.lastname: Allegaert
authors.forename: Heleen J
authors.initials: HJ
authors.lastname: Blussé van Oud-Alblas
authors.forename: Elke H J
authors.initials: EH
authors.lastname: Krekels
authors.forename: Dick
authors.initials: D
authors.lastname: Tibboel
authors.forename: Meindert
authors.initials: M
authors.lastname: Danhof
authors.forename: Catherijne A J
authors.initials: CA
authors.lastname: Knibbe
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001835:Body Weight; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007262:Infusions, Intravenous; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D015742:Propofol / Q000008:administration & dosage / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol