Salivary phenytoin levels in institutionalized epileptics

Measurement of phenytoin (PHT) levels in saliva has been advocated as a monitor of plasma levels, and therefore of effective dosage. All studies to date have been performed on outpatients. We have now analyzed whole saliva from 62 mentally retarded, institutionalized, PHT-treated persons with epilepsy. Both PHT and its major human metabolite, 5-(para-hydroxyphenyl)-5-phenylhydantoin (pHPPH) were measured using gas-liquid chromatography. We detected large inter-individual variations in saliva PHT and pHPPH levels. Data were ranked and subjected to statistical analysis according to Spearman. Significant positive correlations were detected between daily PHT dose and plasma total PHT concentration, plasma PHT and salivary PHT, and daily dose and salivary PHT level. When data were categorized and analyzed according to the type of medication being administered in addition to PHT, different results were obtained. Polypharmacy can influence drug and metabolite levels and relationships in institutionalized persons with epilepsy.