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Pharmacokinetics of theophylline in children with asthma
Insights
Children with asthma eliminate theophylline faster than adults, showing significant interindividual differences. This suggests children may require higher daily doses or more frequent administration of theophylline.
Area of Science:
- Pharmacology
- Pediatrics
- Clinical Pharmacy
Background:
- Theophylline is a bronchodilator used in asthma management.
- Understanding theophylline pharmacokinetics is crucial for effective dosing, especially in pediatric populations.
Purpose of the Study:
- To compare the pharmacokinetics of theophylline in children with asthma versus healthy adults.
- To investigate the elimination rate and half-life of theophylline in these groups.
Main Methods:
- Intravenous aminophylline (4 mg/kg) was administered to 30 children with asthma and 6 healthy adults.
- Theophylline pharmacokinetics, including clearance, half-life, and distribution, were analyzed.
Main Results:
- Children exhibited significantly higher average total clearance (87 ml/hr/kg) compared to adults (57 ml/hr/kg).
- Theophylline's biologic half-life in children varied widely (1.42-7.85 hours) due to interindividual differences in elimination rate.
- Elimination rate constants were considerably higher in children than adults, despite similar distribution parameters.
Conclusions:
- Children with asthma eliminate theophylline more rapidly than adults, with substantial interindividual variability.
- Pediatric asthma patients may necessitate higher daily theophylline doses and/or more frequent dosing intervals compared to adults.
Abstract:
The pharmacokinetics of theophylline following intravenous injection of aminophylline, 4 mg/kg of body weight, were determined in 30 children with asthma and in 6 normal adult volunteers. The average total clearance of theophylline was 87 ml/hr/kg in the children and 57 ml/hr/kg in the adults. The biologic half-life of theophylline in the children ranged from 1.42 to 7.85 hours, reflecting mainly pronounced interindividual differences in the elimination rate constant of the drug. There was no significant difference between the children and adults with respect to the distribution rate constants and apparent volumes of distribution of theophylline, but the elimination rate constant of the drug was considerably higher in children than in adults. Thus, children eliminate theophylline more rapidly on the average than do adults and also show pronounced interindividual differences in the elimination of the drug. Compared to adults, children tend to require relatively larger amounts of theophylline per day and the doses may have to be given at shorter intervals of time.