This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
The digestive principle of the gastric juice, obtained from the mucous membrane of the stomach of the hog, and mixed with powdered sugar of milk.
Solubility. - It is not completely soluble in water, leaving floccules of pepsin floating in the solution, which, however, dissolve on the addition of a small quantity of hydrochloric acid.
Impurities. - Strong turbidity of the acidulated solution indicates the presence of mucus, which also imparts to the saccharated pepsin a disagreeable odour and taste, and will eventually impart to it an ammoniacal odour.
2-4 fl. dr.
Uses. - Pepsin is given as an aid to digestion, when the ordinary stimuli do not excite sufficient secretion, and the digestive ferment is insufficient. Such cases occur during a long illness or during recovery from an acute disease, in old people, and in people with atrophy of the mucous membrane and glands of the stomach, due to alcoholic excesses or long-continued dyspepsia. It may be given either with or just after meals. It has no influence on farinaceous foods or fat, but only acts on gelatinous and albuminous matter; hence it is no use giving it after farinaceous or fatty food.
In these cases the secretion of acid is usually defective, and a little dilute hydrochloric acid given along with pepsin, and again about two hours after meals, is very useful.
In some cases of asthma, dependent on insufficient digestion, pepsin is very useful. Pepsin wines and essences usually contain little or no pepsin, and have little digestive power, but they contain rennet, and are frequently of use in indigestion in children; they also appear serviceable in adults.