Factors affecting theophylline pharmacokinetics in premature infants with apnea

Theophylline disposition was examined in 17 premature neonates (birth weight 760-1,480 g) at cessation of therapy for primary apnea. Mean ± SD of clearance (22.9 ± 3.9 ml/h/kg) and apparent volume of distribution (0.630 ± 0.1501/kg) were somewhat greater than previously reported for newborn infants at 4-15 days. Better correlations were found between maturational factors and clearance adjusted for body surface area than for clearance adjusted for weight. A limited correlation (r=0.53) was found between clearance/body surface area and duration of therapy. No significant differences in pharmacokinetics occurred in patients who received parenteral alimentation. While some variability and age dependence exists in theophylline disposition in newborns, such variability is substantially less than found in older children and in adults.