Hepatic biotransformation capacity in low-birth-weight infants as measured with the [15N]methacetin urine test: influences of gestational age, postnatal age, and intrauterine growth retardation

Biol Neonate. 1995;68(1):19-25. doi: 10.1159/000244213.


The influences of the gestational age (range: 28-36 weeks) and the postnatal age (range: 6-100 days) on the biotransformation capacity of the liver were studied in 51 preterm appropriate-for-gestational-age infants and in 20 preterm small-for-gestational-age infants using the [15N]methacetin urine test. Methacetin is a test drug assessing a two-step pathway of biotransformation including monooxygenation and conjugation. After oral administration of 3 mg [15N]methacetin/kg body-weight, the cumulative 15N excretion in urine during the consecutive 9 h was measured and used as a marker of microsomal biotransformation capacity. In preterm appropriate-for-gestational-age infants, the biotransformation capacity increases with gestational age as well as with postnatal age, but the strongest correlation could be found between cumulative [15N] excretion and postmenstrual age. Intrauterine growth retardation results in lower biotransformation capacity (26.3 +/- 11.3 vs. 36.1 +/- 9.6% [15N] excretion, expressed as percentage of intake) and disturbed postnatal development of this hepatic function. The data indicate that normal intrauterine development is a prerequisite for normal postnatal development of the biotransformation capacity, which might have consequences for the metabolism and efficacy of certain drugs in small-for-gestational-age infants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / administration & dosage
  • Acetamides / urine
  • Biotransformation
  • Fetal Growth Retardation* / urine
  • Gestational Age*
  • Humans
  • Infant
  • Infant, Newborn
  • Infant, Premature / urine*
  • Infant, Small for Gestational Age / urine
  • Liver / enzymology*
  • Oxygenases / metabolism*
  • Prospective Studies


  • Acetamides
  • methacetin
  • Oxygenases