Phenytoin Therapy for Epileptic Children: Evaluation of Salivary and Plasma Concentrations and of Methods of Assessing Compliance

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Abstract
Monitoring phenytoin therapy in children is difficult because they fear blood sampling, yet frequent control of phenytoin levels may be necessary because of the age-dependence of phenytoin metabolism. In 22 patients aged 6-15 yr, phenytoin concentrations were studied in mixed saliva and parotid saliva, and were compared with plasma levels from blood obtained at the same time. For mixed saliva, the saliva:plasma concentration ratio was 0.11 .+-. SD 0.04 and in parotid saliva it was 0.10 .+-. 0.06. Compliance was studied in 13 children, each receiving between 3-7 different quantities of phenytoin. Clinical judgement about compliance agreed well with the 2 laboratory measures. A graphic analysis of the relationship between plasma concentration and dosage is proposed as a practical method of assessing compliance, because it appears to be both simple, reliable and suitable for routine use.