Changes in trimethoprim pharmacokinetics after the newborn period

Arch Dis Child. 1989 Mar;64(3):343-5. doi: 10.1136/adc.64.3.343.


The pharmacokinetics of trimethoprim administered orally or intravenously were investigated in six infants aged 1.7 months to 1.1 years. In these infants trimethoprim had a mean half life of 4.6 hours; this was comparable with the values found in young and school age children (3.8 and 5.4 hours respectively) and about a quarter of the half life in newborns. The volume of distribution (1.5 l/kg) was smaller than in newborns but larger than in young or school age children (0.9 and 1.1 l/kg respectively). The plasma clearance in these infants (3-3 ml/min/kg) was slightly larger than in newborns or in either group of older children (2.9 and 2.4 ml/min/kg respectively). Thus the most dramatic changes in trimethoprim pharmacokinetics seem to occur during the first two months of life. A reduced daily dose of trimethoprim is necessary during the first two months only. An increased daily dose, by addition of a third dose each day, is recommended from two months.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Chromatography, High Pressure Liquid
  • Humans
  • Infant
  • Metabolic Clearance Rate
  • Trimethoprim / blood
  • Trimethoprim / cerebrospinal fluid
  • Trimethoprim / pharmacokinetics*


  • Trimethoprim