Monitoring of phenobarbitone and phenytoin therapy in small children by salivary samples.

Concentrations of phenytoin or phenobarbitone have been measured serially using saliva samples in 75 very young children receiving one of these drugs for prevention of recurrent febrile convulsions. Saliva samples were easily obtained and the measured concentrations were a valuable guide to drug dosage during the treatment period. Mean (+/- SD) saliva concentrations were, for phenytoin, 1.0 +/- 0.8 mg/litre (3.8 +/- 3.0 mumol/litre) and, for phenobarbitone, 7.9 +/- 2.6 mg/litre (24.0 +/- 11.3 mumol/litre) and did not alter significantly during the period of observation. Despite frequent review with assessment of compliance, it proved difficult to achieve and maintain target drug concentrations. Paired samples of saliva and plasma were obtained from 36 children before treatment was terminated. Drug concentrations in saliva correlated well with those in plasma and mean plasma: saliva ratios (phenytoin, 8.4; phenobarbitone, 2.2) were comparable to results obtained previously in adults.