Maturation of AFMU excretion in infants

Fundam Clin Pharmacol. 1989;3(6):589-95. doi: 10.1111/j.1472-8206.1989.tb00461.x.


The maturation of the N-acetyltransferase-dependent AFMU production from caffeine was studied during infancy. The group of children (N = 14) consisted of 4 premature newborn infants and ten 1-19 month-old infants who received caffeine citrate solution for the treatment and prevention of apnea. Caffeine, AFMU, 1X and 9 other metabolites were measured in urine using HPLC. The AFMU/1X ratio did not vary significantly in this population with increasing age. In one of the infants serially studied, the AFMU/1X ratio increased dramatically between 6 and 12 months of age. This observation suggests that the maturation of N-acetyltransferase activity is not completed before 1 year of age implying that acetylator status cannot reliably be determined before that age. Patients studied before 1 year of age whose AFMU/1X ratio was below 0.4 may be either true slow acetylators or still immature fast acetylators.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation
  • Caffeine*
  • Chromatography, High Pressure Liquid
  • Humans
  • Indicators and Reagents
  • Infant
  • Infant, Newborn
  • Infant, Premature / urine*
  • Phenotype
  • Uracil / analogs & derivatives*
  • Uracil / urine


  • Indicators and Reagents
  • Caffeine
  • Uracil
  • 5-acetylamino-6-formylamino-3-methyluracil