Pharmacologia / Fourth American, from the Seventh London Edition

by John Ayrton Paris

SOLID FORMS.

PULVERES. Powders.

The form of powder is in many cases the most efficient and eligible mode in which a medicinal substance can be exhibited, more especially under the following circumstances.

1. Simple Powders.

1. Whenever a remedy requires the combination of all, or most of its principles, to ensure its full effects, as Bark, Ipecacuan, Jalap, &c.

2. Where medicinal bodies are insoluble, and indisposed to undergo those essential changes, in transitu, which render them operative; for it must be remembered that by minute division, every particle is presented to the stomach in a state of activity, being more immediately exposed to the solvent or decomposing powers of that organ.

3. Where the mechanical condition of the substance is such as to occasion irritation[^[294]] of the stomach, as the Sulphuretum Antimonii, or in external applications to produce an improper effect upon the skin, as Hydrargyri nitrico-oxydum.

The degree of fineness to which substances should be reduced by pulverization, in order to obtain their utmost efficacy, is a very important question. The impalpable form appears to be extremely injurious to some bodies, as to cinchona, rhubarb, guaiacum, and to certain aromatics, in consequence, probably, of an essential part of their substance being dissipated, or chemically changed by the operation. Fabbroni, for instance, found by experiment that cinchona yielded a much larger proportion of soluble extractive, when only coarsely powdered. I think it may be laid down as a general rule, that extreme pulverization assists the operation of all substances whose active principles are not easily soluble, and of compound powders whose ingredients require, for their activity, an intermixture; whilst it certainly injures, if it does not destroy, the virtues of such as contain as their active constituent, a volatile principle which is easily dissipated, or extractive matter which is readily oxidized.

2. Compound Powders.

The disintegration of a substance is much accelerated and extended by the addition of other materials; hence the pharmaceutical aphorism of Gaubius, “Celerior atque facilior succedat composita, quam simplex pulverisatio.” Thus several refractory vegetable bodies, as myrrh, gamboge, &c. are easily reduced by triturating them with sugar or a hard gum; and some gum resins, as assafœtida or scammony, by the addition of a few drops of almond oil. Upon the same principle the Pharmacopœia directs the trituration of aloes with clean white sand, in the process for preparing Vinum Aloes, to facilitate the pulverization and to prevent the particles of aloes, when moistened by the liquid, from running together into masses; some dispensers very judiciously adopt the same mechanical expedient in making a tincture of myrrh; so again, in ordering a watery infusion of opium, it will be judicious to advise the previous trituration of the opium with some hard and insoluble substance, as directed in the Pulvis Cornu Usti cum Opio, otherwise its particles will adhere with tenacity, and the water be accordingly unable to exert a solvent operation upon its substance.[^[295]] It is equally evident that in the construction of compound medicinal powders, the addition of an inert ingredient, which the mere chemist might condemn and discard as useless, not unfrequently acts a very important part in the combination, owing to its effects in dividing and comminuting the mere active constituents: the sulphate of potass in Dover’s powder acts merely in dividing and mixing more intimately the particles of opium and ipecacuan: the phosphate of lime appears to act in the same mechanical manner in the Antimonial Powder; so again, in the Pulvis Contrajervæ compositus, the prepared oyster shells may be a necessary ingredient: in the Pulvis Jalapæ compositus of the Edinburgh College, the cream of tartar greatly increases the activity of the jalap, by breaking down its substance and dividing its particles; and Van Swieten observes that the operation of this resinous purgative is improved by bruising it with sugar, and adding some aromatic. The old combination of Pulvis Helvetii consisted of alum and dragon’s blood, and there can be no doubt but that the effect of this latter ingredient, which has been often ridiculed, was to retard the solution of alum in the stomach, in consequence of which the preparation was likely to produce less inconvenience, and could therefore be administered in larger doses; the Edinburgh college has substituted gum Kino in their Pulvis Aluminis compositus, which may have the same effect in modifying the solubility of the alum.