The rapid and skilful preparation of pills, from all the numerous substances of which they are composed, is justly considered to demand the highest qualifications in the practical dispenser. The medicinals employed must be made into a consistent and moderately firm mass, sufficiently plastic to be rolled or moulded into any shape, without adhering to the fingers, knife, or slab, and yet sufficiently solid to retain the globular form when divided into pills. A few substances, as certain extracts, &c., are already in this condition; but the others require the use of an excipient to give them the requisite bulk or consistence. As a general rule, all the constituents of a pill which can be pulverised should be reduced to fine powder before mixing them with the soft ingredients which enter into its composition; and these last, or the excipient, should next be gradually added, and the mixture triturated and beaten until the whole forms a perfectly homogeneous mass. It is then ready to be divided into pills. This is effected by rolling it on a slab, with a pill or bolus knife, into small pipes or cylinders, then dividing these into pieces of the requisite weight; and, lastly, rolling them between the thumb and finger to give them a globular form. A little powdered liquorice-root or starch is commonly employed to prevent the pills adhering to the fingers, or to each other, after they are made. Magnesia, so frequently used for this purpose, is unsuited for pills containing metallic salts or the alkaloids, or other remedies, which are exhibited in very small doses.
Instead of forming the mass into pills by hand, in the manner just referred to, a convenient and simple instrument, called a ‘pill-machine,’ is now generally used by the druggists for the purpose. This consists of two pieces. The first (see fig. 1) is divided into three compartments:—c is a vacant space to receive the divided mass, which is to be rolled into pills:—b is a grooved brass plate, which assists in dividing the mass into pills; and a is a box for containing the powder for covering the pills, and to receive them as they
are formed. The second (see fig. 2) consists of a brass plate (a), grooved to match the plate b in fig. 1, and bounded at both ends by movable projecting plates (b b), containing each two wheels under the ledge of the plate (b); and a wooden back (c), with two handles (d d), to which this plate is affixed. In using this machine, the pill-mass is rolled into a cylindrical form on the front part of it, by means of fig. 2 inverted; the small roll is then laid on the cutting part of the instrument (1, b), and divided by passing fig. 2 over it, the little wheels enabling the latter to run easily on the brass plate which forms the margin of the bed of the machine. The pills, thus formed, are then drawn forward on to the smooth bed on which the mass was first rolled, and receiving a finishing turn or two with the smooth side of the ‘cutter,’ by which they are rendered more nearly spherical. They are, lastly, thrown over into 1, c, ready to be transferred to the pill-box.
Fig. 1 and Fig. 2.
The nature of the excipient should be suited to that of the active ingredients in pills, as well as in all other forms of medicine. Furthermore, it should be of such a nature “that,” to quote Dr Redwood, “it will modify as little as possible the action of the pills, either by causing them to become hard, or in any other way, and will not unnecessarily or inconveniently increase their size.” Soft extracts, and other substances of a like character, may be rendered more consistent by the addition of any simple powder, as that of liquorice or sugar. Vegetable powders are generally beaten up with syrup or treacle, and heavy powders with conserve of roses or extract of liquorice. Castile soap (made of olive oil and soda) and medicinal soft soap (made of olive oil and potash) are commonly employed for fatty and resinous matters, as well as for many others which are not decomposed by alkalies. When the chief ingredient of the mass is resin, rectified spirit is frequently used to soften it, either with or without the addition of soap to increase its solubility in the stomach. For many substances no excipient is required. Thus, most of the gum-resins and stiff extracts
may be at once made into pills, or, at all events, after being slightly softened by heat. Mucilage, formerly so much used in the preparation of pills, is now only employed for those which are to be taken within a day or two after being made; as pills containing it become so hard and insoluble when kept for some time as to resist the action of the stomach, and frequently to pass through the bowels without even losing their form. Glycerin, as well as a mixture of glycerin and tragacanth made into a paste of proper consistence, are also employed as pill-excipients.
The use of glycerin as a pill-excipient has been advocated on account of its generally neutral properties, and also because its substitution for syrup, the conserves of roses, treacle, and such like substances, results in the production of a pill of smaller bulk. It seems to be suited for pills containing chemical substances, such as quinine, tannic acid, &c. It is said, however, to possess the disadvantage of making the pills moist on their surfaces. To obviate as much as possible this inconvenience, and to provide an absorbent for the superfluous moisture, Mr Martendale, an experienced pharmacist, recommends the employment of a mixture of glycerin and flour, of which he writes as follows:—“By stirring constantly and heating together until a temperature of about 240° F. is reached, 5 parts of glycerin by weight, and 1 part of flour, a firm adhesive paste is formed, which I shall call glycerin mass. As an excipient for vegetable powder it answers well, and for other substances on which it can exert a partially solvent action it is eminently useful. Among these are such salts as valerianate of zinc, 4 gr., which with 1 of the glycerin mass forms a good pill.
Quinine, 3 parts, with 1 of the glycerin mass, P. B. strength, works well. Compound powder of ipecacuanha, 5 gr., with 3⁄4 gr. of the mass, makes a good pill. Oxide of zinc, too, 4 gr. with 1, makes a good mass.
But for most mineral and insoluble powders it is too moist, and will not form with them a firm mass; some additional absorbent is necessary, and for this purpose I found nothing better than flour; equal parts of the glycerin mass and flour form a tolerably firm, solid, adhesive paste, somewhat resembling dough, but it is not so elastic; this I call bread mass. It possesses great capacity for the absorption of insoluble powders, such, for example, as calomel (3 gr. with 11⁄2 gr. of this mass makes a good pill), nitrate and carbonate of bismuth, arsenic, &c. Of reduced iron, 3 parts with 2 of it, form a good mass, in which the iron is not liable to oxidation. Carbolic acid, too, of which it is a good solvent, is readily made into a pill with the bread mass, a little additional flour being necessary for this substance. Then again, substances which are given in minute doses, as the salts of morphia, resin of podophyllum, and other active principles to