Diphenhydramine determination in human plasma by gas-liquid chromatography using nitrogen-phosphorus detection: application to single low-dose pharmacokinetic studies.

A highly sensitive method (less than or equal to 1 ng/ml) for single-dose pharmacokinetic studies of diphenhydramine which utilizes GLC with nitrogen-phosphorus detection is described. Standard curves, using orphenadrine as the internal standard, were linear for diphenhydramine concentrations from 1.0 to 300 ng/ml. Applicability of the method was demonstrated by a pharmacokinetic study in a normal volunteer who received 25 mg iv of diphenhydramine.