This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Papain is a ferment obtained from the Carica papaya, from which exudes, on incision, a white, slightly astringent and milky juice, which contains the papain. It has the taste of pepsin and is soluble in water and glycerol.
Papain is a digestive ferment like pepsin, its active digestive power causing the solution of albuminous substances. Catillon denies that it is a true ferment, with power to convert albuminoids into peptones; hence it cannot be substituted for pepsin in affections of the stomach; it is active in an acid, neutral or faintly alkaline solution.
It is an active solvent of false membranes, intestinal worms, ascarides and taenias, hence it is employed in diphtheria, ascarides, vermiculares, tapeworm. Locally, like pepsin, it is employed in the form of injections made with a hypodermic syringe, in the treatment of fatty tumors and other benign growths, and to retard the growth of cancerous and other malignant tumors, the solution being injected well into the substance of the tumor.
Papain is employed in the treatment of ulcers and tumors of the mouth, both benign and malignant, the solution being injected into the substance of the growth by means of a hypodermic syringe; it has also been used to digest portions of a pulp, requiring from 24 to 72 hours, the cavity well secured. Dr. Harlan states that if one gram of papain is made into a thick paste with glycerol and a drop of hydrochloric acid solution (1-300), is added, it always acts well in pulp-digestion, prior to the removal from the roots of teeth of dead pulp-tissue.