Salicylic Acid (HC7H5O3 = 137.05) is a monobasic acid obtained from Oleum Betuloe, or made synthetically by treating phenol with sodium carbonate and carbon dioxide.

Pharmacodynamics.

Central Nervous System. - Slight stimulation, followed by depression, of the medulla, and possibly of the cord.

Muscular System. - No effect.

Respiration. - First increased, then slowed; action centric.

Heart is accelerated, by direct action; but is weakened and slowed by large doses, chiefly from local action.

Blood-pressure is increased as a result of a stimulation of the vasoconstrictors; falls after large doses (centric ?).

Eye. - Sight is disordered from changes in retinal cells.

Ear. - Hearing is disordered from alterations in the tympanum.

Alimentary Tract. - Irritated.

Secretory Glands. - Sweat-glands stimulated from irritation of heat center. Renal epithelium and liver-cells are stimulated.

Metabolism. - There is an augmented decomposition of protein and endogenous uric acid; also, an increase of leucocytes.

Temperature is decreased in fever through an action on the heat center causing a dilatation of the cutaneous vessels.

Absorption is rapid from stomach and intestines as the sodium salt.

Excretion takes place chiefly by way of the kidneys and in the form of salicyluric acid. It is entirely eliminated in 48 hours.

Local Action. - Salicylic Acid is an irritant, even to the point of necrosis. Protoplasm is poisoned; protein and glucoside ferments are inhibited in their action.

Symptoms.

Therapeutic Doses.

Fullness in the head. Buzzing in the ears. Slight giddiness.

Toxic Doses.

Mental confusion. Disturbances of sight and hearing. Excessive perspiration. Dyspnea. Slow, weak pulse. Subnormal temperature. Hematinuria. Collapse. Respiratory failure.

Therapeutics.

Salicylic Acid, and its salts, have been employed successfully in the treatment of acute rheumatic fever. Its action in rheumatic fever is not understood.

Dosage.

Acidum Salicylicum, 0.3 to 2 Gm. Sodii Salicylas, 0.6 to 2 Gm. Phenylis Salicylas, 0.5 to 2 Gm.

Salicylic Acid 81

Crimson = stimulation Green = irritation. Violet = depression.