Poudres, Fr.; Puvern, G.; Polveri, It.; Polvos, Sp.
The form of powder is convenient for the exhibition of substances which are not given in very large doses, arc not very disagreeable to the taste, have no corrosive property, and do not deliquesce rapidly on exposure.
With regard to keeping powders in well-stoppered bottles, it is asserted by Herouard, a French pharmacist, that this plan, instead of preserving some powders, tends to their more speedy and certain change. Whatever pains may be taken in drying drugs previously to powdering them, most of them during the process attract moisture, so as to put themselves in this respect in equilibrium with the surrounding air; and, if enclosed in this state in air-tight vessels, they are exposed to injurious influence from their own absorbed water, which, vaporized in hot weather, is in the colder seasons condensed on the inner surface of the vessel and determines a movement of fermentation, and even cryptogamic growths appear in some instances. The best method of preservation, the author thinks, is to enclose the powders in strong paper bags of a 'blue or gray color, so as to exclude the light, while the air has exit or entrance through the porous walls. Whatever may be our theoretical opinions on the point, Herouard asserts the fact, as the result of observation, that powders keep best in this way, and his statement coincides with our own experience. The powders may be more likely to cake or harden into aggregate masses; but this disadvantage is easily counteracted by a new pulverization when required. (J. P. C., Aout, 1862, p. 98.) From these statements the inference may be drawn that, where powders are kept in air-tight bottles, they should be thoroughly dried, after pulverization, before being enclosed, and many, such as ergot, rhubarb, etc., should be kept in paper boxes or cartons.
In relation to substances most liable to injury from these causes, the best plan is to powder them in small quantities as wanted for use.
Powders may be divided into the simple, consisting of a single substance, and the compound, of two or more mixed together. The latter only are embraced under the present head. In the preparation of the compound powders, the ingredients, if of different degrees of cohesion or solidity, should be pulverized separately and then mixed. Deliquescent substances, and those containing fixed oil in large proportion, should not enter into the composition of powders intended to be kept,—the former because they render the preparation damp and liable to spoil, the latter because they are apt to become rancid and impart an unpleasant odor and taste. When deliquescent substances are extemporaneously prescribed, the apothecary should enclose them before delivery in waxed paper or other impervious covering; and the same remark is applicable to volatile powders, as ammonium carbonate and camphor. The lighter powders may in general be administered in water or other thin liquid; the heavier, such as those of metallic substances, require a more consistent vehicle, as syrup, molasses, honey, or one of the confections. Resinous powders, if given in water, require the intervention of mucilage or sugar. For many powders the cachet de pain affords the best method of administration.
These very useful articles are wafers made of unleavened bread in such a manner that they offer a concavity, so that when two are placed face to face there is a space in which a powder may be contained. They are of different sizes and capacities, the largest readily holding as much as ten grains of quinine. In filling them, one wafer is placed upon a board, and the requisite amount of medicine is put in it; then a second wafer, whose interior margin has been wetted, is laid upon the first and pressed down upon it. When taken, they should be dipped in water, placed immediately upon a teaspoon containing a little water, and swallowed with a gulp of fluid. For most powders of disagreeable taste, cachets afford the best method of administration.
Gelatin capsules are extensively used for the administration of drugs in powdered form and are admirably adapted for this purpose if the dose is not too large, as they are readily filled and easily taken by the patient.
In the act of powdering, the whole substance in the mortar should not be beaten until completely pulverized, as the portion already powdered interferes with the action of the pestle upon the remainder, while the finer matter is apt to be dissipated, so that there is a loss of time and of material. The proper plan is to sift off the fine powder after a short continuance of the process, then to return the coarser parts to the mortar, and to repeat several times this alternate pulverization and shifting, until the process is completed. Care should be taken to mix thoroughly the several portions of fine powder thus obtained.