Penflutizide ‎is a thiazide diuretic drug, Na+-Cl- symport inhibitor. Penflutizide was shown to have high potency to photooxidize lipids. Penflutizide -photosensitized peroxidation of squalene was repressed by the presence of sodium azide or 2,5-dimethylfuran and was accelerated in a D2O suspension. These findings suggest the participation of singlet oxygen in Penflutizide photoperoxidation of squalene (type II mechanism). Penflutizide -photosensitized lysis of red blood cells (RBC) accompanied by formation of hydroperoxides in RBC membrane lipids was also noted. These results suggested that membrane lipids can be one of the target molecules of Penflutizide phototoxicity. Penflutizide ‎is an ingredient of the drug Praemenstron manufactured by Nordmark Arzneimittel and consisting of Flumedroxone, Meprobamate, Penflutizide.