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Phenytoin serum levels in children with epilepsy: a micro immuno-assay technique
Insights
Twice-daily dosing of phenytoin (5mg/kg/day) is recommended for children with seizures to maintain adequate serum levels. Higher doses (10mg/kg/day) may be necessary for seizure control in some cases.
Area of Science:
- Pediatric Neurology
- Clinical Pharmacology
Background:
- Phenytoin is a common antiepileptic drug used in children.
- Optimizing phenytoin dosage is crucial for effective seizure management and minimizing adverse effects.
Purpose of the Study:
- To evaluate the pharmacokinetics of phenytoin in children with seizures.
- To determine optimal dosing strategies for phenytoin therapy in pediatric epilepsy.
Main Methods:
- Enzyme multiple immuno-assay technique (EMIT) was used to measure phenytoin serum levels.
- Fifty children with seizures were included in the study, with varying dosage regimens and prior medication histories.
Main Results:
- Single daily doses of phenytoin (5mg/kg/day) resulted in inadequate serum levels.
- Twice-daily dosing (5mg/kg/day) achieved adequate therapeutic phenytoin serum levels in most children.
- Increasing the dose to 10mg/kg/day improved seizure control in some children.
- Phenytoin serum levels reached equilibrium in 5 days in children not on phenobarbitone, but took 1-4 weeks in those previously on phenobarbitone.
- Proper suspension preparation (shaking well) was essential for achieving satisfactory serum levels.
Conclusions:
- Twice-daily administration of phenytoin is recommended for pediatric seizure management.
- Dosage adjustments and consideration of prior medication (phenobarbitone) are necessary for achieving therapeutic phenytoin levels.
- Phenytoin demonstrated stable serum levels during long-term follow-up (14-30 months).
Abstract:
The enzyme multiple immuno-assay technique (EMIT) was used to study phenytoin serum levels in 50 children with seizures. It was found that: (1) a single dose of phenytoin suspension or capsules (5mg/kg/day) produced inadequate serum levels 16 and 24 hours after ingestion, and for this reason single dosage is not recommended; (2) twice-daily dosage of phenytoin suspension or capsules (5mg/kg/day) produced adequate serum levels in most children throughout the 24 hours, and this dosage is recommended; (3) 12 children continued to have seizures but when the dose was increased to 10mg/kg/day six of the 12 obtained control of seizures; (4) phenytoin reached equilibrium in the serum in five days provided the child had not previously been taking phenobarbitone; (5) of 13 children who had been taking phenobarbitone, 10 did not achieve equilibrium of phenytoin in serum for one to four weeks; (6) phenytoin suspension given twice-daily produced satisfactory serum levels provided the bottle was shaken well before dispensing; (7) apart from minor variations, phenytoin maintained its level in serum during the 14 to 30 months follow-up period, whether 5mg or 10mg/kg/day of phenytoin was given.