Effects of diphenhydramine and famotidine on lipid peroxidation and activities of antioxidant enzymes in different rat tissues.

The potential antioxidant activity of diphenhydramine (histamine H1-receptor antagonist) and famotidine (histamine H2 receptor antagonist) was studied. Diphenhydramine inhibited the spontaneous, Fe(II)-induced and Fe(II)/ascorbate-induced lipid peroxidation, while famotidine showed a biphasic concentration-dependent effect on spontaneous lipid peroxidation (a stimulation by 1 mM and an inhibition by 5 mM) and increased Fe(II)-induced- and inhibited Fe(II)/ascorbate-induced lipid peroxidation in the rat liver and brain. Both drugs decreased *OH-provoked deoxyribose degradation in Fenton-type systems and inhibited O2- -provoked reduction of nitro-blue tetrazolium and ferrycytochrome C, but famotidine effect was stronger than that of diphenhydramine.