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Theophylline pharmacokinetics in premature infants with apnea
Insights
Theophylline elimination is slow and variable in low-birth-weight infants treated for apnea. Careful monitoring and adjusted dosing are crucial for safe and effective theophylline therapy in neonates.
Area of Science:
- Neonatal Pharmacology
- Pediatric Clinical Pharmacy
Background:
- Apnea is common in low-birth-weight infants.
- Theophylline is used to treat primary apnea in neonates.
Purpose of the Study:
- To characterize the pharmacokinetics of theophylline in low-birth-weight infants.
- To provide dosing recommendations for theophylline in this population.
Main Methods:
- Eight low-birth-weight infants received theophylline for apnea.
- Theophylline levels were measured using high-pressure liquid chromatography.
- Pharmacokinetic parameters including half-life, volume of distribution, and clearance were calculated.
Main Results:
- Theophylline exhibited a prolonged half-life (13-29 hours) and a large volume of distribution (0.65-2.86 L/kg).
- Body clearance of theophylline was low (23-68 mL/hr/kg).
- Significant variability in theophylline elimination was observed.
Conclusions:
- Theophylline elimination is extremely slow and variable in low-birth-weight infants.
- Therapeutic drug monitoring and individualized dosing are essential.
- A suggested initial regimen includes a loading dose of 6 mg/kg and a maintenance dose of 2 mg/kg every 12 hours, adjusted for maturation.
Abstract:
The pharmacokinetics of theophylline were examined in eight low-birth-weight infants (gestation: 26-32 weeks: birth-weight: 887-1,480 gm), who received the drug for treatment of primary apnea. The drug was assayed by high pressure liquid chromatography. The final dosage was 1 to 3 mg/kg/6 hour at 25 to 37 days of age. At the time, theophylline had a prolonged half-life ranging from 13 to 29 hours, a relatively large volume of distribution of 0.65 to 2.86 1/kg, and a small body clearance of 23 to 68 ml/hr/kg. The extremely slow and variable elimination of theophylline must be considered in treatment of apneic infants. The initial dosage regimen suggested is a loading dose of 6 mg/kg and a maintenance dose of 2 mg/kg/ 12 hours, with adjustments made based on monitoring of the serum concentration and on an increased biotransformation capability as maturation occurs.