Gamma irradiation effects on diphenhydramine hydrochloride: an EPR study

Abstract

This study seeks to detect and characterize the free radicals generated in gamma-irradiated diphenhydramine hydrochloride (DP-HCl), a precursor for an antihistamine drug. The investigation aims to assess the radiation sensitivity of DP-HCl under varying microwave power, radiation doses, temperature conditions, and storage durations. After irradiation with 14 kGy, the observed radical associated with the –ĊHCH2N– fragment exhibited a singlet signal with a g-value of g = 2.0016 ± 0.0005. The signal intensities from experimental spectra within the 2–20 kGy dose range were found to exhibit the optimal fit with a polynomial function. Experimental spectra were recorded in the temperature range of 123–423 K to investigate whether distinct types of radicals were formed at low and high temperatures. Furthermore, the stability of the free radicals generated in the irradiated sample was assessed by determining the extinction curves of the signal intensities of the sample. The novelty of this study lies in examining the radiation sensitivity of the –ĊHCH2N– radical, demonstrating its remarkable stability across different temperatures and storage durations. This leads to the conclusion that radiation sterilization of the DP-HCl sample is not suitable.