Origin. - An organic acid usually obtained by subjecting milk sugar or grape sugar to lactic fermentation. It is composed of 75 per cent. by weight of absolute lactic acid (CHC3H5O3 = 89.79) and 25 per cent. of water.

Description and Properties. - A colorless, syrupy liquid, odorless, of a purely acid taste, and absorbing moisture on exposure to damp air. Specific gravity about 1.206 at 25 C. (77o F.). Freely miscible with water, alcohol, or ether; insoluble in chloroform, benzin, or carbon disulphide.

Dose. - 20-30 minims (1.2-1.8 Cc), diluted and sweetened. [30 minims (2 Cc), U. S. P.].

Official Preparation

Syrupus Calcii Lactophosphatis - Syrupi Calcii Lactophosphatis - Syrup of Calcium Lactophosphate. - Formula: Precipitated calcium carbonate, 25; lactic acid, 60; phosphoric acid, 36; orange-flower water, 55: sugar, 725; water, q. s. ad 1000. Dose, 1-2 fluidrams (3.7-7.3 Cc.) [2 fluidrams (8 Cc), U. S. P.].

Antagonists and Incompatibles. - Alkalies and the salts of the mineral acids are incompatible with lactic acid.

Synergists. - Pepsin, vegetable acids, hydrochloric acid, and sodium chloride.

Physiological Action. - Externally and Locally. - Lactic acid is a caustic to highly organized tissues, resembling the mineral acids in its local action. It can dissolve false membrane.

Internally. - Digestive System. - It is thought to be present in the stomach during the first forty-five minutes of stomachic digestion, but cannot be considered a normal constituent of the gastric juice.

Circulatory System. - Being absorbed from the stomach, it combines with bases in the blood, forming lactates which are rapidly converted into carbonates.

Nervous System. - Large doses are thought to depress the nervous system.

Absorption and Elimination. - It is absorbed from the stomach, undergoes a change in the blood, and is eliminated by the kidneys, although, according to Lehmann, when large doses have been taken it is found in the urine unchanged; and we have Benzelius and Scherer as authorities that lactic acid can be detected in the spleen and the muscular fluid. It has been found in the exudates in puerperal fever.

Untoward action, poisoning, and treatment of poisoning are similar to those of the mineral acids.

Therapeutics. - Externally and Locally. - It has been used locally for the same purposes as the mineral acids, but it is thought by many clinicians to be superior to the latter in tuber-culous ulceration.

As a solvent of false membranes lactic acid is unquestionably superior to the mineral acids, being highly recommended for this purpose in diphtheria and croup by many authorities.

Internally. - Digestive System. - It is used in the digestive disorders, such as atonic and irritative dyspepsia, and in all those derangements of digestion which are benefited by hydrochloric acid. In oxaluria, lithemia, chronic cystitis with ammoniacal urine, chronic dysentery, and dyspeptic and tubercidous diarrhea it has proved an efficient remedy. It has been recommended as a prophylactic in gout.

Since this drug was suggested by Cantani as a remedy in diabetes mellitus it has been used with varying success. Balfour and Foster, as well as Cantani himself, have reported many cases which have greatly improved under the administration of lactic acid accompanied by an appropriate dietetic regimen.

Contraindications. - The same as for mineral acid. Administration. - Lactic acid should be given well diluted.