Saccharated Tar, or Soluble Vegetable Tar.
By M. A. ROUSSIN.
The value of vegetable tar as a therapeutic agent is generally recognized, but hitherto, in consequence of the small extent to which it is soluble in water, its use has been limited. Many attempts have been made to secure a greater solubility, but this has only been obtained by the employment of alkalies,—that is to say, by saponification. But saponification undoubtedly modifies the elements of the tar, and partly destroys its curative properties.
According to M, Adrian, "these preparations do not correspond by their chemical composition to the therapeutic properties that are expected in them," and he states that he has found alkalies, as well as acids, to modify the resinous qualities that are the basis of the medicament.
Dr. Jeannel has expressed a similar opinion. He says it is necessary that the tar should be emulsed by a neutral substance, since, by so doing all the natural properties of the tar would be preserved.
Impressed with the correctness of this idea, M. Roussin sought to adapt to vegetable tar the same process by which he was able, on a former occasion, to form an emulsion with balm of copaiba. ("Annales du Comité Médical des Bouches-du-Rhône," t. v. p. 67.) At that time he proposed to use sugar for facilitating the emulsion of copaiba in water, and as a corrective of the repulsive taste of that substance. Sugar being a neutral substance, without any chemical action capable of modifying the composition or curative properties of medicinal substances; and daily associated without hesitation with all kinds of remedies.
After several attempts this problem was resolved, and a complete solution of the vegetable tar in water obtained. The emulsion of tar was effected by triturating in a porcelain mortar, so as to obtain a homogeneous paste, purified tar, powdered sugar and powder of gum arabic. A small quantity of water was added to obtain an emulsion; it was then left to stand, and afterwards decanted. This saccharated emulsion had not the repulsive odor of the emulsion prepared with alkali; it possessed the odor of tar, and a taste neither sharp nor bitter. It was miscible with water in all proportions, so that, by estimating the quantity of tar present, a solution might be prepared instantaneously, containing any required quantity of the active principle.
But the liquid form of the medicament presenting many and serious inconveniences, it appeared to M. Roussin that the pulverulent form, with all its practical advantages, would be very desirable. He therefore pursued his researches until he succeeded in obtaining a saccharate, as a yellow powder only differing from sugar in appearance by its color, and exhaling the balsamic odor of tar. This preparation constitutes a remedy essentially new in form, and appears to be the real and complete solution of the problem of Dr. Jeannel.
The saccharate of tar is constant in its composition. It contains 4 per cent. of purified vegetable tar. A teaspoonful (5 grammes) thus represents 20 centigrammes of tar, and will suffice for the preparation of a litre of water.
According to M. Bouchardat, 30 grammes of tar-water contain nearly 1 centigramme of the principles of the tar in solution. This would be nearly 30 centigrammes to the litre. Soubeiran says that the proportion of matter dissolved in tar-water is so small that 100 grammes do not contain 4 centigrammes (less than 40 centigrammes the litre), and that patients can scarcely support the tar-water unless it be diluted.
The irritation of the stomach often provoked by the tar-water of the Codex is prevented by the saccharate; the proportion being but 4 per cent., the acridity of the tar is covered. Another advantage, not less important, due to its pulverulent form, is that it avoids the necessity of swallowing a large quantity of liquid, since a glass of water is sufficient to dissolve several teaspoonfuls. The physician can thus augment the quantity of tar according to the necessities of the patient.
The pulverulent form has another valuable advantage. Patients who are unable to overcome the repugnance the odor and taste of tar often provoke, may enjoy the benefits of this therapeutic agent by making up the saccharate into a pill with unleavened bread.
Gay, speaking of the acridity and repulsive taste of oil of tar, recommended that it should be sweetened, "in order to mask its flavor and its odor." Sugar, as I have said, does not alter the therapeutic properties, but modifies its organic properties and facilitates its absorption. While retaining the odor and taste of the remedy, the saccharate so disguises them that the most delicate stomachs can bear it without repugnance.
The saccharate of tar is not the result of a chemical reaction; it is a simple mixture, each of the elements of which retains intact its composition and its properties. Constant in its composition, it will furnish solutions really and mathematically entitled to the name, being able to fulfil all the conditions necessary for mixtures, gargles, injections, etc., and enabling the physician to give his patient such quantity of tar as he may deem necessary.—Pharm. Journ. and Trans., Sept. 23, 1871., from Journal de Pharmacie et de Chimie.