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Carbamazepine population pharmacokinetics in children: mixed-effect models
M F Delgado Iribarnegaray1, D Santo Bueldga, M J García Sánchez
1Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Salamanca, Spain.
Insights
Carbamazepine clearance in children with epilepsy is influenced by body weight, age, and dose, with phenobarbital also affecting it. This study developed a model for accurate pediatric dosing recommendations.
Area of Science:
- Pharmacokinetics
- Pediatric Epilepsy
- Drug Metabolism
Background:
- Carbamazepine (CBZ) is a widely used antiepileptic drug in children.
- Understanding factors influencing CBZ clearance is crucial for optimizing pediatric dosing and therapeutic outcomes.
- Previous studies have shown variability in CBZ pharmacokinetics among pediatric populations.
Purpose of the Study:
- To investigate the impact of various factors on carbamazepine (CBZ) clearance (CL) in children with epilepsy.
- To develop and validate a population pharmacokinetic model for CBZ in pediatric patients.
- To provide a basis for accurate CBZ dosage recommendations in children.
Main Methods:
- Analysis of 387 steady-state serum CBZ concentration samples from 201 children (aged 1-14 years).
- Utilized NONMEM software with a one-compartment model for population CL calculation.
- Evaluated total body weight (TBW), age, dose, sex, and comedications (phenobarbital [PB], valproic acid [VA]) as covariates.
Main Results:
- CBZ CL increased linearly with TBW and nonlinearly with age.
- CBZ CL also increased with dose, suggesting dose-dependent autoinduction.
- Concomitant PB administration significantly affected CL, while sex and VA did not.
Conclusions:
- A validated population pharmacokinetic model accurately predicts CBZ CL in children.
- The model highlights the importance of TBW, age, dose, and PB comedication for pediatric CBZ dosing.
- The findings support the development of precise CBZ dosage guidelines for pediatric epilepsy management.
Abstract:
The aim of the authors' study was to investigate the factors affecting carbamazepine (CBZ) clearance (CL) in children with epilepsy. The factors evaluated were total body weight (TBW), age, dose, sex, and phenobarbital (PB) and valproic acid (VA) comedication. A total of 387 steady-state serum concentration samples was analyzed. These were collected during CBZ therapy from 201 children, aged 1-14 years and weighting 9-78 kg. Population CL was calculated by using NONMEM, with a one-compartment model with first-order absorption and elimination. The absorption rate, bioavailability, and volume of distribution were set at values found in the literature. The model found best to describe the data was CL = (0.0122 TBW + 0.0467 Dose) Age0.331 (1.289 PB). The interindividual variability in CL had a variation coefficient (CV) of 11.8%, and the residual error, described by using an additive model, was 1.5 mg/l. The results show that CL increases linearly with TBW and nonlinearly with age; thus older children have a lower CL with respect to TBW than do younger ones. Likewise CL was seen to increase with the increase in the CBZ dose, suggesting a dose-dependent autoinduction of CBZ metabolism. Concomitant PB administration affected CL: however, sex and VA comedication did not affect it significantly. The final regression model for CL, was validated in a different group of 74 children. The standarized prediction error (SPE) was not significantly different from zero (SPE = 0.028), indicating that the model proposed for CL can be used to make accurate dosage recommendations. With these population estimates, CBZ doses that would be suitable for pediatric patients of different ages are proposed.