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Maturational changes of theophylline pharmacokinetics in preterm infants
C I Dothey1, K Y Tserng, S Kaw
1Department of Pediatrics, Case Western Reserve University, Cleveland Metropolitan General Hospital, OH 44109.
Insights
Theophylline clearance in preterm infants increases logarithmically with postnatal age during the first six months of life. Postnatal age is the strongest predictor of theophylline half-life (t1/2) in neonates.
Area of Science:
- Neonatal pharmacology
- Pediatric pharmacokinetics
- Drug metabolism in infants
Background:
- Theophylline is a bronchodilator used in neonatal respiratory conditions.
- Understanding theophylline pharmacokinetics is crucial for safe and effective dosing in preterm infants.
- Infant maturation significantly impacts drug metabolism and elimination.
Purpose of the Study:
- To investigate the pharmacokinetics of theophylline in preterm infants.
- To determine the influence of maturational variables on theophylline's half-life (t1/2) and clearance.
- To identify key predictors of theophylline disposition in the neonatal period.
Main Methods:
- Stable isotope methodology was employed to study theophylline pharmacokinetics at steady state.
- Nine preterm infants were monitored during the first six months of life.
- Statistical analyses, including correlation and stepwise multiple regression, were performed.
Main Results:
- Theophylline half-life (t1/2) showed strong logarithmic correlations with postnatal age (r=0.98) and postconceptional age (r=0.96).
- Postnatal age emerged as the most significant predictor of theophylline t1/2 (partial r=0.78).
- Gestational age, treatment duration, and body weight did not significantly correlate with pharmacokinetic parameters.
Conclusions:
- Theophylline metabolizing function in the infant liver increases logarithmically during the first six months of life.
- Postnatal age is a critical factor in predicting theophylline elimination in neonates.
- These findings support age-based adjustments for optimizing theophylline therapy in preterm infants.
Abstract:
The pharmacokinetics of theophylline were studied at steady state by stable isotope methodology in nine individual preterm infants. Maturational variables such as postnatal age, postconceptional age, gestational age, duration of treatment, and body weight at the time of the study were analyzed for their influence on theophylline kinetics during the first 6 months of life. The strongest statistical correlations were found between the logarithm of theophylline half-life (t1/2) and the postnatal age (r = 0.98; p less than 0.001) and the postconceptional age (r = 0.96; p less than 0.001). Step-wise multiple regression analysis revealed postnatal age as the most powerful predictor for theophylline t1/2 in the neonatal period (partial correlation coefficients were 0.78 for postnatal age, 0.19 for postconceptional age, and 0.10 for gestational age). Gestational age, duration of treatment, and weight did not correlate significantly with any pharmacokinetic parameters. We propose that theophylline metabolizing function of the liver increases in a logarithmic fashion during the first 6 months of life.