Pharmacokinetics of theophylline in infancy.

Theophylline clearance rates and half-life values were measured in 15 infants aged three to 23 months, after infusion of aminophylline by the intravenous route for at least 24 hours. The mean clearance rate was 1.07 +/- 0.55 ml/min-kg, which is comparable with values obtained by others in older children. There was some correlation of clearance rates with age. The mean half-life was 4.4 +/- 2.2 hours. There was a tenfold variability in half-life, suggesting that individualization of theophylline dose is especially important in infants if undertreatment and toxicity are to be avoided.