External

Formerly arsenous acid was used as a caustic to destroy growths, lupus, warts, etc., either pure or as a paste. Marsden's paste consists of arsenous acid, 1; powdered acacia, 2 parts. Arsenous acid, 1; charcoal, 1; red mercuric sulphide, 4 parts; and water, sufficient to make a paste, is a formula once very popular. It must be used strong enough to make the mass of dead tissue slough out quickly, or else the patient becomes poisoned, for the arsenic is rapidly absorbed. Arsenous acid, 1; calomel, 8; vermilion antimony sulphide, 8 parts; make a caustic powder. Liquor potassii arsenitis has been recommended by Ringer as an application for corns.

Internal

Alimentary canal. - Arsenous acid is useful to destroy the tooth pulps before filling teeth.

In some forms of dyspepsia small doses of Liquor Potassii Arsenitis are occasionally given to stimulate the appetite. Arsenic is so liable to cause sickness, diarrhoea, and other symptoms of poisoning, that it is a rule always to begin a course of it with small doses, say 3 or 4 minims .20 to .25 c.c. of Liquor Potassii Arsenitis, or 1/60 to 1/40 gr. .001 to .0015 gm. of arsenous acid as a pill, and to gradually increase the quantity. Arsenic in any form should always be taken immediately after meals, so as to dilute it by the contents of a full stomach. Children bear it well; old people do not. Very small doses sometimes check vomiting, especially that form in which the food simply regurgitates, and in exceptional cases it may succeed in checking diarrhoea when other drugs have failed.

Remote Effects

Arsenic is of great value in chronic superficial skin diseases not owing their cause to an irritant. It is, therefore, largely used for psoriasis, pemphigus, and sometimes for chronic eczema. It is of no use in the acute stages of these maladies, nor if cutaneous inflammation is deep-seated.

Cases of anaemia which cannot be cured by iron, and which fall under the heading of primary anaemia, may be occasionally much improved by arsenic. Such are pernicious anaemia, splenic leucocythaemia, and Hodgkin's disease; but often no drug is of any avail. In other forms of anaemia, such as chlorosis, arsenic may be tried, but not often with benefit, when iron compounds disagree. It often improves the metabolism, the appetite, and the weight in those whose general health is feeble. Arsenic is, next to quinine, the best antiperiodic we have; but it is not nearly so efficacious. It may, however, in the absence of quinine, be used for ague, and is especially valuable for the anaemia which follows ague, and for neuralgia due to the same cause. It often does distinct good in rheumatoid arthritis if given for a long while. It is frequently prescribed for chorea, particularly in rapid increasing doses; but it is difficult to prove that the patients get well more quickly than they would without any drug. Arsenic has been strongly recommended in asthma and in hay fever. For asthma it may be given by the mouth, or smoked as cigarettes, made by saturating bibulous paper in a solution of fifteen grains 1. gm. of potassium arsenite to an ounce 30. c.c. of water. It has been given in phthisis, but without benefit. There appears to be good evidence that arsenic in large doses restrains the growth of sarcomata, particularly of the fusiform-cell variety. The springs of Levico and La Bour-boule contain arsenous acid. Strong Levico contains 1/12 gr. .005 gm. of arsenous acid and 30 gr. 2. gm. to the pint 480. c.c. Weak Levico 1/120 gr. .0005 gm. and 8 gr. 0.5 gm. respectively. La Bourboule contains 1/12 gr. .005 gm. of arsenous acid and a trace of iron to the pint 480. c.c. These waters should always be drunk at meals.

Cacodylic acid (AsO(OH)O(Ch3)2, (not official), and sodium cacodylate (AsONa(Ch3)2, (not official) have recently been proposed as eligible methods for the administration of arsenic. The former contains 58 per cent. of arsenic. Then solubility, relatively small toxicity and the diminished local irritation which they produce are advantages to be borne in mind. The best form of administration is as sodium cacodylate given hypodermatically in daily amount of from 3/4 to 2 1/2 gr.; .05 gm., .15 gm., in solution. By this method the arsenic is fully efficacious, no alliaceous odor is given to the breath or perspiration, and gastric and intestinal disturbances do not supervene. Prolonged use may set up albuminuria. By the rectum it produces less irritation and the odor of garlic is not so pronounced as after the use of Fowler's solution. This method is preferable in the treatment of tuberculosis, diabetes, Basedow's disease and leukaemia.