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Carbamazepine and carbamazepine-epoxide serum protein binding in newborn infants

J B Groce, D T Casto, P Gal

    Therapeutic Drug Monitoring
    |January 1, 1985
    PubMed

    Insights

    Neonates show lower serum protein binding for carbamazepine (CBZ) but similar binding for its metabolite carbamazepine-10,11-epoxide (CBZ-E). Monitoring free CBZ concentrations is recommended due to variable binding in newborns.

    Area of Science:

    • Pharmacology
    • Neonatal Medicine
    • Clinical Chemistry

    Background:

    • Carbamazepine (CBZ) is an anticonvulsant medication used to treat epilepsy and other conditions.
    • Understanding drug-protein binding is crucial for determining effective and safe therapeutic ranges, especially in vulnerable populations like newborns.
    • Previous studies have established protein binding characteristics of CBZ and its epoxide metabolite (CBZ-E) in adults and older children.

    Purpose of the Study:

    • To evaluate the extent of serum protein binding for carbamazepine (CBZ) and its active metabolite carbamazepine-10,11-epoxide (CBZ-E) in newborn infants.
    • To compare neonatal protein binding of CBZ and CBZ-E with existing data from older populations.
    • To assess the clinical implications of neonatal drug binding, particularly regarding therapeutic drug monitoring.

    Main Methods:

    • Cord serum samples were collected from 20 newborn infants at birth.
    • Samples were spiked with known concentrations of CBZ and CBZ-E.
    • Total and free drug concentrations were analyzed using high-performance liquid chromatography (HPLC) after ultrafiltration to determine unbound fractions.

    Main Results:

    • Neonates exhibited a mean unbound fraction of 30.6% for CBZ at higher concentrations and 29.8% at lower concentrations.
    • The mean unbound fraction for CBZ-E in neonates was 52.0% at higher concentrations and 47.5% at lower concentrations.
    • Compared to adults and older children, neonates showed significantly lower protein binding for CBZ, while CBZ-E binding was comparable.

    Conclusions:

    • Neonatal serum protein binding of CBZ is lower than in older individuals, suggesting a potential need for adjusted therapeutic ranges.
    • CBZ-E binding in neonates is similar to that observed in older populations.
    • Due to observed variability in binding, monitoring free CBZ serum concentrations in neonates is advisable for optimizing therapy.

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