Dichlorophenarsine is a potent anti-syphilitic drug, which exhibits a rapid effect on the serological reactions of the blood in early syphilis. Dichlorophenarsine was more rapid than thiacetarsamide sodium in its action against the canine heartworms infections. Dichlorophenarsine was used for the treatment of canine filariasis - emesia, nausea, and shock occurred several to 30 minutes after injection. Ascorbic acid and hesperidin methyl chalcone when used as a combined therapy afforded a definite protection in mice against the toxic effect of a single dose of intravenously administered dichlorophenarsine hydrochloride.