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Fluctuations in steady-state phenytoin concentrations as measured in saliva in children
Insights
Salivary phenytoin concentrations in epileptic children fluctuated significantly, with a 52% mean peak-to-trough difference. Saliva levels were 56% higher on days medication was taken before sampling, impacting clinical management.
Area of Science:
- Pharmacokinetics
- Clinical Pharmacy
- Pediatric Neurology
Background:
- Phenytoin is a common antiepileptic drug.
- Understanding drug concentration variability is crucial for effective treatment.
- Salivary phenytoin monitoring offers a non-invasive method to assess drug levels.
Purpose of the Study:
- To evaluate salivary phenytoin concentrations in epileptic children on monotherapy.
- To assess the impact of medication timing on drug levels.
- To explore the relationship between phenytoin concentrations and potential behavioral effects.
Main Methods:
- Hourly salivary phenytoin concentrations were measured in children receiving twice-daily phenytoin.
- Drug concentrations were compared between days when medication preceded or followed sample collection.
- Peak-to-trough fluctuations in steady-state concentrations were analyzed.
Main Results:
- Rapid phenytoin absorption was observed, with peak concentrations typically occurring 1-5 hours post-morning dose.
- Significant daily fluctuations in steady-state salivary phenytoin concentrations were noted (mean 52% peak-to-trough).
- Salivary phenytoin levels were substantially higher (mean 56% difference) when medication was taken before sampling.
Conclusions:
- Salivary phenytoin monitoring can reveal significant drug concentration variability in children.
- Timing of medication administration relative to sampling significantly impacts salivary phenytoin levels.
- These findings have implications for optimizing phenytoin dosing and monitoring its behavioral effects in pediatric epilepsy.
Abstract:
Data from two studies are reported. In the first, salivary concentrations were monitored hourly in epileptic children receiving phenytoin monotherapy, twice daily. The results indicated rapid drug absorption in the majority with time of maximum concentration occurring most frequently 1-5 hours following morning medication. A number of children showed moderate to large fluctuations in steady-state drug concentrations during the day, and there was a mean peak-to-trough fluctuation of 52% over the group. In the second study, drug concentration data are reported from an ongoing investigation of phenytoin's behavioral effects. Medication was given before sampling on one day, whereas it was delayed until after sample collection on the alternate day. Results indicated that salivary concentrations were higher, for 38 of 41 subjects, on the expected-high day with an overall mean difference in drug concentration of 56% between the 2 days. These findings were discussed in terms of their implications for clinical management and the possible relation of drug concentrations to psychomotor function.