Arsenic is widely distributed in nature and can be detected in many of our commonly used chemicals and even in certain chemic drugs. It is said to appear in the fruit of trees sprayed with Paris green, and in other plants grown in the soil where Paris green has been used.

Preparations And Doses

(A) Those Of Arsenous Acid

Arsenic trioxide, arsenous acid, white arsenic, As2O3, is an anhydride which occurs as a practically odorless and tasteless white powder, made either from the glassy variety, soluble in 30 parts of water, or from the porcelain or crystalline variety, soluble in 100 parts of water. Both dissolve in 5 parts of glycerin and are sparingly soluble in alcohol. Dose, 1/30 grain (0.002 gm.).

Solution of arsenous acid, liquor acidi arsenosi, 1 per cent., is acid with hydrochloric acid. Dose, 3 minims (0.2 c.c.).

Fowler's solution, liquor potassii arsenitis, KAsO2.HAsO2.H20, 1 per cent., contains the compound tincture of lavender to give it distinctive odor, taste, and color as a preventive against accidents. Dose, 3 minims (0.2 c.c.). This is the favorite liquid preparation. It is incompatible with acids, and tends to oxidize and deteriorate.

Arsenous iodide, Asl3; dose, 1/12 grain (0.005 gm.).

Donovan's solution, liquor arseniet hydrargyri iodidi, contains

1 per cent. each of arsenous iodide and mercuric iodide. Dose,

2 minims (0.12 c.c.).

(B) Those Of Arsenic Acid

Sodium arsenate, Na2HAsO4,-7H20; dose, 1/12 grain (0.005 gm.).

Dried sodium arsenate, sodii arsenas exsiccatus, is sodium arsenate deprived of its water of crystallization by heat. As this water constitutes about two-fifths of the arsenate, the drying nearly doubles the strength. Dose, 1/20 grain (0.003 gm.).

Solution of sodium arsenate, 1 per cent. of the dried salt; dose,

3 minims (0.2 c.c).

(c) Besides the official preparations, there are a number of organic compounds that are in use:

Sodium arsanilate (sodium aminophenyl arsonate) is employed in the form of atoxyt, C6H4(Nh2).(AsO.OH.ONa) + 3H2O, containing 3 molecules of water of crystallization and 26 per cent. of arsenic; and soamin, C6H4(Nh2).(AsO.OH.ONa) + 5H2O, which contains 5 molecules of water of crystallization and 22 per cent. of arsenic. They are white powders, soluble in 5 or 6 parts of water, and decomposed by acids. Because of the acidity of the gastric juice, they are given hypodermatically. Dose, 1/3 to 3 grains (0.02-0.2 gm.) every second day.

Arsacetin Is Sodium Acetyl Arsanilate, C6h4(Nhch3co)

(AsO.OH.ONa), soluble in 10 parts of cold water and 3 parts of hot water. It can be sterilized in the autoclave at 130o C. for one hour without decomposition. The claim is made that it is not split up by acids. The hypodermatic dose is 3 grains (0.2 gm.) two or three times a week. By mouth the dose is 3/4 grain (0.05 gm.) three or four times a day.

Arsenophenylgtycin, As2(Cooh.Ch2.N.H.C6H4)2, has a hypodermatic dose of 12 grains (0.8 gm.).

Sodium Cacodytate, Sodium Dimethyl Arsenate, (Ch3)2aso

ONa + 3H2O, is readily soluble in water. It liberates arsenic quite slowly, hence is less toxic and less active than the inorganic salts. Dose, 1 grain (0.06 gm.) hypodermatically, or 3 grains (0.2 gm.) by mouth daily. A hypodermic of 4 to 6 grains (0.25-0.35 gm.), repeated in four days, was recommended by John B. Murphy in syphilis. Recently doses of 1 to 7 1/2 grains (0.06-0.5 gm.) intravenously have been used in pernicious anemia, leukemia, and Hodgkin's disease. A number of other compounds of caco-dylic acid have also been employed, as those of iron, mercury, quinine, lithium, etc. Owing to the formation of cacodyl oxide, the cacodylates are prone to give a garlicky odor to the breath, especially when administered by mouth.

Salvarsan, Ehrlich's "606," is diamino-dihydroxy-arseno-benzol dihydrochloride, (C6H3As.OH.Nh2hcl)2. It is a bright yellow powder, of strongly acid reaction, and completely but slowly soluble in 10 parts of water. It is used somewhat hypodermatically, but preferably intravenously. Before use it must be freshly made into a sterile solution of slightly alkaline or neutral reaction. It is very readily oxidized, so is kept in vacuo, or in ampules filled with an indifferent gas. The maximum dose is 10 grains (0.6 gm.), which for intravenous use is dissolved in 300 c.c. of normal saline to which 23 drops of 15 per cent, sodium hydroxide solution are added. Diarsenol, a recent substitute for salvarsan, made in Canada, is claimed to be the dihydrochloride of dioxydiamidoarsenobenzol, and is administered in the same way as salvarsan.

Neo-salvarsan, soluble in water and of neutral reaction, and therefore available by simple solution, may be administered with much greater ease. It is sodium-diamino-dihydroxy-arseno-benzol-methanal sulphoxylate mixed with half its weight of inert substance. Its dose is 1 1/2 times that of salvarsan. It deteriorates very quickly, so must be kept in vacuo. Sodium-salvarsan, a similarly soluble compound, is recommended highly by Wechselmann and by Dreyfus.

Pharmacology

Microorganisms

Arsenic is added to embalming mixtures to prevent rapid decomposition. It is more destructive, however, to highly organized life than to bacteria.

Local

Arsenic is irritant. It does not precipitate protoplasm and does not form an albuminate, but slowly acts on the tissues to produce inflammation. An arsenic paste, for example, causes pain, redness, and swelling, with fatty degeneration of the epithelium and inflammation of the tissues beneath. The inflammatory reaction may be so intense that destruction of tissue follows, with sloughing and the formation of an ulcer. The drug is, therefore, a slowly acting and very painful caustic, which destroys tissue, not by precipitating protoplasm, but by inducing an acute inflammatory reaction. In its use to destroy the nerves of teeth the destruction of the nerve depends upon inflammation and swelling in the opening of the root of the tooth, so that the circulation of the nerve is cut off.