Salicylic acid is prepared synthetically by treating a solution of carbolic acid in caustic soda with carbonic acid, at a moderate heat. It is also found in nature in oil of wintergreen, in sweet birch, and in the bark of several varieties of willow. A dull white powder, readily soluble in alcohol and glycerin, but almost insoluble in cold water. In hot water it is more readily dissolved, and borax and boric acid assist the solvent action.

Physiological Actions

Salicylic acid is an antiseptic and disinfectant. If is a diaphoretic and antipyretic in fever, but does not lower the temperature in health. It is not much used in this way, as other antipyretics are more lasting in influence and less depressing than salicylic acid.

After an antipyretic dose there is slight temporary stimulation of the heart; the face and eyes are suffused and there is a feeling of warmth, followed by perspiration. These effects are visible in ten or fifteen minutes, and following them there is a reduction of the strength of the heart.

Salicylic acid has a stimulant and disinfectant action on the kidneys and urinary apparatus, and increases the acidity of the urine. In some cases it irritates the kidneys and causes haematuria or albuminuria.

In small doses it stimulates digestion, the heart, and respiration, but in large doses it depresses the last two, lowers arterial tension, and causes nausea and vomiting.

Incidental Effects

In giving salicylic acid the first evidences of overdosing which are to be looked for are buzzing and roaring in the ear, and fulness of the head. Increased doses bring severe headache, perspiration, deafness, and various disturbances of vision; and, if still continued, these symptoms are all intensified. The respirations become deeper and are labored, rapid, and irregular - sometimes the most violent respiratory efforts being made to overcome the dyspnoea; the pulse is slow and weak, and there is a great restlessness, with a delirium characterized by hallucinations of vision, and which is sometimes cheerful, sometimes melancholy, and sometimes wildly maniacal. The urine may be dark olive-green, and involuntary evacuations of the bowels may take place.

The depression of the circulatory system causes a relaxed state of the skin, and bed-sores are liable to appear rapidly. Eruptions of the skin, somewhat resembling that of urticaria, may appear even after medicinal doses.

Salicylic acid is not considered an active poison to man. Cases of death from its use have been recorded, but they are not all well verified. As a preservative in canned foods it acts as a slow poison and as such it is even more dangerous.

Salicylic acid is transformed in the blood into salicylate of sodium, and is slowly excreted by the urine, perspiration, saliva, bile, and mucous secretions.

Average dose, gr. xii.-0.75 Gm., moderately diluted.

Sodii Salicylas. Sodium Salicylate

Made by the action of salicylic acid on carbonate of sodium. It is readily soluble in water; has the same physiological actions as salicylic acid, and is less irritating. It has no antiseptic qualities in external use. It is considered a specific in rheumatism, and in giving a course of it the same incidental symptoms mentioned under salicylic acid are to be looked for. Average dose, gr. xv.-I Gm., moderately diluted.

Phenylis Salicylas. Phenyl Salicylate. Salol

A preparation composed of two thirds salicylic and one third carbolic acids. It is insoluble in water and is given in compressed tablets.

Salol is antiseptic and antipyretic; sedative to the brain and spinal cord, and with some power as an analgesic. It is an active diaphoretic, and though in some cases it has a somewhat depressing effect, yet its action is usually not marked by as much exhaustion as that of many of the new antipyretics, and when the temperature rises after being reduced by salol, it does so without chill or chilly feelings. Its physiological effects and medicinal uses are in general very like those of salicylic acid. It is not considered poisonous, and is, like iodoform, used as a topical application.

Average dose, gr. v.-0.3 Gm.

Salicin. Oleum Gaultheriae. Thiersch Powder

See Organic Materia Medica.

A combination of salicylic and boric acids, usually ordered in the proportion of ℥ ss. of the latter to ʒ ss. of the former. Added to one quart of water it forms an antiseptic solution, of moderate power, which is not irritating or poisonous when freely used. The proportions of a Thiersch powder are not invariable, as Prof. Thiersch did not confine himself to one formula.1

Theobrominae Sodio-Salicylas. Theobromine Sodio-Salicylate

Made from theobromine, an alkaloid obtained from the seeds of Theobroma cacao, the chocolate tree of South America, and sodium salicylate. It is a white powder, soluble in half its weight of warm water. As the theobromine separates from it on exposure to the air, it should not be given as powder, but as freshly prepared aqueous solution.

Physiological Actions

It is a reliable diuretic, increasing the amount of urine, and the solids excreted by the urine. Its influence over the amount of albumin is not constant. However, in chronic nephritis the amount of albumin is generally diminished. In dropsy, with the increase of urine, there is disappearance or marked improvement of the oedema. Occasionally a profuse diarrhoea is apparently produced by the remedy, and assists in this removal of the transudation.

It is believed that the drug has a moderate influence on the heart. It strengthens and regulates it, is not depressing, and produces no functional disturbance. It does not appear that it causes any irritation either of the stomach or kidneys. Its diuretic action depends on a direct influence on the renal epithelium.

Average dose, gr. viii.-0.5 mils.

1 Charles Rice, Ph.D.