Michaelis-Menten pharmacokinetics of diphenylhydantoin and application in the pediatric age patient

Michaelis-Menten pharmacokinetics were evaluated for diphenylhydantoin given to 104 patients 0.5 to 16 years of age with seizures. A method for individualizing the dosage regimen of DPH for each patient was evaluated retrospectively. The Vmax was inversely related to age (r = 0.552, P less than 0.001) but there was no such relationship for Km. The individual pharmacokinetics were characteristic of that person and could be used to adjust dosage so that toxicity would be avoided. We present a nomogram for adjusting the dosage of DPH in the pediatric age groups.

Micro-determination of total phthalate esters in biological samples by gas-liquid chromatography

A method was investigated in which all of the phthalate esters in biological samples were determined as phthalic acid by gas-liquid chromatography. The method is based on the separation of phthalate esters from the sample with n-hexane, saponification of the esters with an alkaline ethanolic solution to give phthalic acid, purification of the acid by extraction with diethyl ether and column chromatography using silica gel, and conversion of the acid into bis(2,2,2-trifluoroethyl) phthalate with a 2,2,2-trifluoroethanol solution containing boron trifluoride. The derivative obtained is highly sensitive to an electron-capture detector, giving a sensitivity of 0.1 pg. Biological samples fortified with di(2-ethylhexyl) phthalate at levels of 5-100 ppb were analyzed, with recoveries of 70-100%.