Acidum Acetyl-Salicylicum. Acetyl-Salicylic Acid.

Related entry: Salicylic acid - Methyl salicylate

C9H₈O₄ = 180.064.
Synonyms.—Acidum Acetosalicum; Acetosalic Acid; Acetosalin; Acidum Salaceticum; Salacetin.

Acetyl-salicylic acid, C₆H4(COOH)OCOCH3, is prepared by the action of acetic anhydride or acetyl chloride on salicylic acid. It was originally introduced into medicine under the trade-name Aspirin. It is also known, in a simple or compounded form, under the trade-names Acetysal, Aletodin, Saletin, Xaxa, etc. It occurs in colourless acicular crystals, or as a white, crystalline powder. melting-point (when dry), 135°. The acid should be free from chlorides and sulphates, and leave no residue on ignition. If 1 decigram (10 gram) be dissolved in 5 mils of alcohol, 20 mils of water added, and then 1 drop of dilute ferric chloride solution, a violet colour should not be produced immediately (absence of free salicylic acid). The acid should be preserved in well-closed bottles, and kept in a dry place.

Soluble in water (1 in 300), alcohol (1 in 5), ether, or chloroform.

Action and Uses.—Acetyl-salicylic acid passes through the stomach unchanged, but is slowly decomposed by the alkali of the duodenum, salicylic acid being liberated. It has therefore the same action as salicylic acid (see Acidum Salicylicum), but is less liable to produce objectionable secondary effects such as gastric disturbance. The powder is applied locally at frequent intervals in the early stages of tonsillitis. It is best administered in cachets, powders, or tablets, and should not be prescribed with alkaline substances. The aqueous and alcoholic solutions decompose on standing, salicylic and acetic acids being formed; the reaction takes place very rapidly in alkaline solutions. For administration to children the powder may be mixed with cold milk. Compressed tablets of acetyl-salicylic acid sometimes contain some free salicylic acid, produced by contact with water during manipulation; this may be avoided by the use of ethereal solution of wax or theobroma for granulation.

Dose.—½ to 1 gramme (8 to 15 grains).

PREPARATION.

Tablettae Acidi Acetyl-salicylici, B.P.C.—ACETYL-SALICYLIC ACID TABLETS.

5 grains. Given for all forms of rheumatism. Dose.—1 to 3 tablets.

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.