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The effect of phenobarbital on theophylline disposition in children with asthma

C L Saccar, M Danish, M C Ragni

    The Journal of Allergy and Clinical Immunology
    |June 1, 1985
    PubMed

    Insights

    Phenobarbital significantly increases theophylline clearance in children with asthma, reducing serum concentrations. Dosage adjustments are necessary when these drugs are used together to maintain therapeutic theophylline levels.

    Area of Science:

    • Pharmacology
    • Pediatric Medicine
    • Clinical Pharmacy

    Background:

    • Theophylline is a common asthma medication.
    • Phenobarbital is an anticonvulsant that can affect drug metabolism.
    • Concurrent use of theophylline and phenobarbital in pediatric asthma patients requires investigation.

    Purpose of the Study:

    • To investigate the effect of chronic phenobarbital administration on theophylline disposition in children with asthma.

    Main Methods:

    • Seven children with asthma were studied.
    • Theophylline clearance was measured before and after 19 days of phenobarbital (2 mg/kg/day) dosing.
    • Steady-state serum theophylline concentrations were monitored.

    Main Results:

    • Little variability in baseline theophylline clearance was observed.
    • Phenobarbital significantly increased apparent theophylline clearance (0.104 vs. 0.077 L/hr/kg).
    • Mean steady-state serum theophylline concentration decreased by 30% (12.0 vs. 8.4 µg/ml).

    Conclusions:

    • Phenobarbital induces theophylline metabolism in pediatric asthma patients.
    • Theophylline dosage adjustments are likely needed for concurrent use.
    • Maintaining therapeutic theophylline levels requires consideration of phenobarbital's effect.

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