Acetyl-salicylic acid, or aspirin, C6H4.O.Coch3.Cooh, of slightly sour taste and acid reaction, is soluble in 125 parts of water and freely in alcohol. It gives no reaction with ferric chloride, unless previously decomposed by alkalies or boiling with water. On boiling with 10 per cent. sodium hydroxide solution it separates into its components.

In many instances it has proved less irritant to the stomach than either salicylic acid or sodium salicylate, but not infrequently it causes hyperacidity with heartburn, or nausea or vomiting. The claim is made that it passes through the stomach unchanged, and is decomposed in the alkaline intestinal contents to form sodium salicylate and sodium acetate; but sodium carbonate in a test-tube does not so decompose it. Theoretically, it should not be given with sodium bicarbonate or other alkali, lest it be decomposed in the stomach; but in the author's experience the bicarbonate lessens the nausea and heartburn which sometimes result from its use.

Acetyl-salicylic acid has greatly replaced quinine in the affections of the profession and the laity, and is prescribed or taken in 5-grain (0.3 gm.) tablets or capsules every two or three hours for colds, sore throat, neuralgia, headache, and influenza. It is also used wherever a salicylate is indicated. Williamson (1902) found that it reduced the sugar in the urine in a number of cases of diabetes, but not in the severe cases, but Hall found that 60 grains (4 gm.) a day for twenty-seven days was without any effect. It is strongly diaphoretic.

Toxicology

There are a number of reports of angioneurotic swelling of the face and throat, or general urticaria, with or without nausea, vomiting, dizziness, and collapse. These are due to idiosyncrasy, and have usually followed small doses, such as 15 grains (1 gm.). Von Noorden (1912) says that in three of his cases acute nephritis followed the use of aspirin. When in long contact in solution quinine and acetyl-salicylic acid form quino-toxin, a substance possessing some of the actions of digitoxin. A death from this cause is reported.

Novaspirin is the methyl-citric-acid ester of salicylic acid; diplosal is the salicylic-acid ester of salicylic acid; and diaspirin is succinyl disalicylic acid. It is claimed for all these that they pass through the stomach unchanged.

Salol, or phenyl salicylate, C6H4.OH.Cooc6h5, is in the form of crystals with a characteristic aromatic odor. It gives a violet color with ferric chloride. It is soluble in alcohol, but is insoluble in water and practically insoluble in gastric juice. In a test-tube alkalies produce the odor of phenol, and in the alkaline contents of the intestine it is decomposed and goes into solution as sodium salicylate and phenol. These products are rapidly absorbed and are excreted in the urine as salicyluric acid and phenol sulphonates. Whether or not they have an antiseptic effect in the intestine is a moot question, most observers, with the exception of Herter, perhaps, having failed to note a diminution of the indican, or any other indication of diminished putrefaction.

Indeed, phenol itself, judging from the work of Richards and Howland, is more prone to increase than to lessen the symptoms of auto-intoxication. Salol is sometimes carried through the intestines without change, the odor being recognized in the feces.

In its customary dose of 5 grains every three or four hours salol can have but little salicylic effect, and it is really a phenol drug rather than a salicylate. It is antipyretic and analgesic, however, and is frequently given with phenacetin for colds or influenza. In chronic colitis it is given in capsules with a few minims of castor oil, e. g., 5 grains (0.3 gm.) of salol and 5 minims (0.3 c.c.) of castor oil. In diabetes, Teschemacher (1901) noted a decided lessening of the sugar in 6 out of 9 cases. He gave 15 grains (1 gm.) four times a day.

As shown in experimental infections, the products in their excretion tend to render the urine antiseptic; hence it is employed in infections of the urinary tract.

Salophen is salicylic-acetanilid. Dose, 15 grains (1 gm.).

Saliphen is salicyl-para-phenetidin.

Malakin is salicyliden-para-phenetidin.

Mesotan is methyl-oxymethyl ester of salicylic acid, with the properties of a volatile oil. It is more irritant than methyl salicylate, so is used diluted with an equal quantity of olive oil.

Spirosal is monoglycol ester of salicylic acid, has also the properties of a volatile oil, and is used in alcoholic or oily solution.

Salicin is a glucoside obtained from willow and poplar barks, It is bitter and is not nauseating. In either the stomach or the duodenum it splits up to form salicyl alcohol and other close relatives of salicylic acid. (See Glucosides, Part I.) Its use is confined to the milder rheumatic manifestations, or to conditions of the stomach which prevent ordinary salicylic medication. Dose, 20 grains (1.3 gm.).

Administration

The volatile oil types of salicylate are applied locally over the inflamed parts either by rubbing or on a compress. Internally they are given in capsules. Aspirin, salicin, salol, etc., are best given in capsules, but may be employed in tablet form.