New antiepileptic drugs for children: felbamate, gabapentin, lamotrigine, and vigabatrin

Population pharmacokinetics of gabapentin in infants and children

PURPOSE

To characterize gabapentin pharmacokinetics in infants and children using a population approach and to identify important demographic and/or physiologic determinants of gabapentin disposition.

METHODS

Gabapentin was administered in single doses of 10 mg/kg (N=48 healthy subjects, age 1 month-12 years) or in multiple doses of 10-65 mg/kg per day (N=205 patients with epilepsy, age 2 months-13 years) at 08:00, 14:00, and 20:00. Serial concentration-time data from the healthy subjects were combined with sparse data obtained in patients and were modeled using NONMEM.

RESULTS

Gabapentin oral clearance (l/h) was directly related to creatinine clearance (ml/min) with a slope of 0.116. The slope of the relationship was 36% greater in blacks than in subjects of other races. When oral clearance was normalized for body weight, young children (<5 years) had higher and more variable values than older children. Volume of distribution was related to body weight and appeared to differ between subjects and patients. Intersubject variability was approximately 30% for oral clearance and volume of distribution and was larger for the absorption rate constant and lag time. Residual variability, a measure of intrasubject variability and measurement error, was smaller in subjects than in patients.

CONCLUSIONS

On a weight basis, 33% larger doses would be required in younger children (<5 years) to achieve the same exposure as older children.

Treatment of childhood epilepsy

Epilepsy in children is frequently misdiagnosed and inappropriately managed with major medical, social, and educational consequences. The advent of the newer anti-epileptic drugs has paradoxically, and in contrast to what was expected, contributed to a therapeutic confusion, which in certain instances, has perpetuated this unsatisfactory management. The purpose of this paper is to address some of the diagnostic and management issues and outline drug regimens for specific seizures types and epilepsy syndromes. Alternative and surgical therapies, and the treatment of neonatal and 'febrile seizures' and status epilepticus will not be discussed in detail, as these particular aspects fall outside the remit of this paper.