title: Chemical stability of diphenhydramine hydrochloride from an elixir and lidocaine hydrochloride from a viscous solution when mixed together.
abstract: The stability of diphenhydramine hydrochloride (from an elixir) and lidocaine hydrochloride (from a viscous solution) in a mixture (1:1) was studied using a stability-indicating high-peformance liquid chromatographic assay method. The concentrations of the drugs were related directly to peak heights and the percent relative standard deviations based on five injections were 1.4 for diphenhydramine and 1.3 for lidocaine. The products of hydrolysis from the both the drugs and a number of excipients present in the dosage forms did not interfere with the developed assay procedure. The mixture was stable for at least 21 days when stored in amber-colored bottles at room temperature. The pH value of the mixture remained constant, and the physical appearance did not change during the study period.
authors: Pharmaceutics Division, University of Houston, Houston, Texas.
authors: Vishnu D
authors: VD
authors: Gupta