Formerly official as Arsenous Acid

Properties : Arsenic trioxid occurs as an opaque, white powder or in irregular masses of two varieties, one amorphous, the other crystalline, opaque and colorless like glass. Arsenic trioxid is very slowly soluble in water and practically insoluble in alcohol (1:30 to 1:100). It dissolves quite readily in solutions of acids or alkalies.

Incompatibilities: Solutions of arsenic are incompatible with salts of iron and of magnesium, lime-water and vegetable astringents.

Action and Uses: Local External Effects and Uses: Arsenic trioxid applied to denuded or ulcerated tissue has a mildly caustic action which is quite painful. It has been used as a caustic, especially to malignant growths, but the painful character of the applications, the danger of absorption, and the uncertain extent of the destructive action have justly limited its use.

Internal Actions: Arsenic trioxid irritates the mucous membrane of the stomach and intestines. Toxic doses cause nausea and vomiting and colicky pains in the abdomen. It produces a diarrhea of a watery character resembling that of cholera. In small doses it produces fatty degeneration of the liver and other internal organs; large doses produce great depression, and collapse may ensue.

Arsenic in therapeutic doses is employed in the treatment of neuralgia. It is thought to be especially adapted to cases of a periodic character. It is also useful in the treatment of chorea. Larger doses, especially if long continued, may cause peripheral neuritis. Arsenic stimulates the action of the blood-forming organs, especially the bone-marrow. It is especially useful in the treatment of pernicious anemia, leukemia and Hodgkin's disease. In these diseases it must be used in as large doses as can be borne. While improvement occurs in these conditions under the use of arsenic it is usually only temporary.

Many skin-diseases are favorably influenced by proper doses of arsenic. It acts by stimulating the skin, in such cases as usually require external stimulating applications. It is also of service in lesions due to disturbances of innervation in which the skin is usually poorly nourished. The following skin affections may be mentioned as likely to be benefited by arsenic: psoriasis, lichen planus, chronic eczema, pemphigus, dermatitis herpetiformis, chronic urticaria and disturbances of the sweat function. On the other hand, acute inflammatory conditions of the skin are made worse by arsenic.

Arsenic is recommended in chronic bronchitis and emphysema. It has been used with apparent good results in tuberculosis. Too great dependence, however, should not be placed on it in the latter affection. It is used in asthma by way of the stomach and in the form of cigarettes.

Arsenic is a powerful remedy against protozoal affections. These include malaria, syphilis and relapsing fever. In the form of arsenic trioxid it has been used successfully in malaria, particularly in the chronic form and in malarial cachexia. See Salvarsan.

Dosage: For ordinary affections of metabolism or for a tonic influence the dose may vary from 0.001 to 0.002 gm. or 1/60 to 1/30 grain. In diseases of the blood the dosage should be regulated according to the effect, but it is well to use as large doses as the patient will tolerate. Arsenic may be used in increasing doses until symptoms of mild intoxication appear. One may begin with 0.005 gm. or 1/20 grain of arsenic trioxid three times daily, and increase by 0.001 gm. or 1/60 grain three times daily. In using Fowler's solution the initial dose may be 3 minims three times daily and increase by 1 minim three times daily. A slight toxic action is indicated by nausea, colicky pains or a puffiness under the eyes. The presence of albumin in the urine may also be observed. Such symptoms may make advisable the temporary withdrawal of the remedy.