Inorganic and organic compounds of mercury and arsenic have long been used in the treatment of disease, due to pathological conditions of the blood. Most of these diseases are caused by the existence of bacteria in the blood stream, chiefly of the family known as the Protozoa. To this type of maladies belong sleeping sickness, syphilis, and malaria; in animals, surra, dourine, tsetse fly disease, etc.Of the several diseases mentioned above, there is no doubt but that syphilis has been the most dangerous, and far-reaching in its effect on mankind, and the one giving the chief incentive to the study of compounds useful in the treatment of diseases of this type.It must be remembered, however, that the compounds to be spoken of in this paper, were not always tried out on animals and human subjects infected with syphilis, but in many cases other members of the Protozoa group were the parasites, notably those causing sleeping sickness. The pharmacology of these drugs is, therefore, not in an altogether satisfactorv condition to make any great generalizations with accuracy as yet.One of the earliest derivatives of arsenic or organic nature to be used was Atoxyl, para-aminophenyl arsenic acid (sodium salt) :
NH1-C&-AsO(ONa)zThis compound was used with some success in the treatment of sleeping sickness and syphilis, but was found very toxic to the host, and often led to blindness, so that it is very little used a t present.Salvarsan, 606, or chemically p,p'-dihydroxy-un,m'-diamino-arseno benzene hydrochloride, a derivative of Atoxyl, has been the most successful in the treatment of syphilis, of the many organic derivatives of arsenic prepared t o date: HCI-NH~-OH-CGH~-AS = As-C6HTOH-NHz-HClAs to the results obtained by the use of this compound, and the method of administration, all are familiar, as well as with its newer derivative, Neosalvarsan; the sodium formaldehyde sulphoxylate salt of Salvarsan, mixed with some sodium sulphite :HO-NHzCsH3-As = As-CeH3-OH-N€I-CH2SO2Na