Ethosuximide Plasma Concentrations: Influence of Age and Associated Concomitant Therapy
The relationship between oral dose and plasma concentration of ethosuximide was evaluated retrospectively in 198 epileptic patients aged 2.5 to 34 years. Age appears to be a major factor in determining the ethosuximide plasma level/dose (L/D) ratio. Children younger than 10 years had mean L/D ratios significantly lower (p<0.0003) than adolescents (10 to 15 years of age) and adults (16 to 34 years of age). Associated antiepileptic therapy reduced the ethosuximide L/D ratio; mean ethosuximide L/D ratios were significantly lower in patients also taking primidone (p < 0.0005) or valproic acid (p < 0.02). The correlation between the dose of ethosuximide administered and the plasma concentration was significant in the 3 age groups considered (p < 0.0004), but the wide scattering of individual plasma concentrations makes it impossible to predict what plasma concentration of ethosuximide will be obtained after a given dose. For this reason, routine monitoring of ethosuximide plasma concentrations still appears to be necessary, especially in children and patients on polytherapy.
KeywordsPlasma Concentration Valproic Acid Antiepileptic Drug Imide Phenobarbitone
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