Pills are uniformly medicated spherical masses, varying from about ⅛ to ¼ inch in diameter, and usually weighing from 1 to 5 grains. They are prepared from masses of special consistence by methods which do not call for detailed description. Pill masses are mechanical mixtures produced by incorporating medicinal liquids, solids, or compounds, by manipulation or machinery, with suitable inert vehicles, termed excipients, the process usually necessitating the use of considerable friction. The quantities given in the Metric and in the Imperial Weights and Measures in the subjoined formulae are those sufficient for the preparation of a convenient number of pills, the exact number being indicated in each formula, In some instances the quantity indicated for a particular ingredient cannot conveniently be weighed on the ordinary dispensing scales. In such cases the usual practice of dispensers should be followed. If, for example, 3/25 grain of atropine sulphate be required for twelve pills, 1 grain of the sulphate is accurately weighed and triturated with 24 grains of milk sugar, and of this mixture 3 grains (= 3/25 grain of atropine sulphate) is used in making with the other ingredients the mass, which is divided into twelve pills. The selection of excipient or excipients, and the determination of the proportion most fitted to yield a typical pill mass, with any specified substance or compound, demands careful consideration on the part of the manipulator, the selection of a suitable excipient being essential to the efficiency of the pills. Pill masses should be thoroughly plastic, and sufficiently firm to retain, when made into pills, a spherical shape, and plasticity for a reasonable period of time.
Excipients vary considerably in their physical characters. They are usually either viscous or liquid fluids, powdered gums, vegetable powders containing mucilage, absorbent vegetable powders, or powdered inert chemical substances. Suitable excipients are suggested in the descriptions of most of those substances which can be administered in the form of pills. The principal excipients in general use and the purpose for which they are chiefly employed are dealt with in this section.
Alcohol is used for rendering camphor and resinous extracts or substances tractable. 1f used alone as an excipient for substances soluble in alcohol, the pills produced are often liable to collapse when kept, unless prevented by the presence of powdered liquorice root and a small quantity of tragacanth (about ¼ grain to each 5-grain pill). Extracts soluble in water can be satisfactorily massed with diluted alcohol (60 per cent. or 45 per cent.) with the addition of powdered gum acacia or tragacanth.
Althaea (Marshmallow Root) contains 25 to 35 per cent. of mucilage. In fine powder it forms a combined absorbent and adhesive. If used too freely the masses produced are liable to become insufficiently plastic. Powdered althaea mixed with 25 per cent. of powdered tragacanth, used sparingly, forms a valuable combination for hardening soft masses.
Castor Oil, in conjunction with powdered soap, is sometimes used for massing camphor, and with alcohol forms the excipient ordered for compound pill of mercurous chloride.
Confection of Roses.—The cohesive power of this excipient is too small to admit of extensive use.
Distilled Water is the official excipient in compound pill of colocynth. Pills containing an appreciable quantity of aloes or water-soluble extracts can be prepared with water as an excipient, if manipulated rapidly. As a general rule it is inadvisable to use as excipients substances which are good solvents for the ingredients to be massed without employing in conjunction small quantities of substances such as powdered tragacanth or gum acacia, or powdered liquorice root, to prevent subsequent falling.
Glucanth (see Tragacanth) possesses considerable cohesive power and is less liable to produce elastic masses than is glycerin of tragacanth.
Glycerin forms a useful addition to pills containing substances (such as iron salts or tannic acid) which render them liable to harden excessively. In consequence of its hygroscopic nature glycerin is rarely used alone.
Glycerin of Tragacanth is an excellent excipient, when used sparingly, for many white chemical substances and for triturations of potent substances with powdered milk sugar. A quantity, just sufficient to impart a crumbling condition should be employed and plasticity obtained by finishing with a trace of liquid glucose or syrup of glucose. Glycerin of tragacanth used alone is liable to produce, unless used sparingly, elastic masses which are difficult to convert into spherical pills.
Gum Acacia in powder is powerfully cohesive in the presence of moisture. Small quantities (usually from ¼ to ½ grain to each 5-grain pill) often prove useful when employed in conjunction with other excipients, especially in the production of masses from gritty material. If used too freely the resulting pills harden excessively.
Kaolin (Bolus Alba) is used as an absorbent powder, and in the form of kaolin ointment for the preparation of pill masses containing substances (such as potassium permanganate, silver nitrate or oxide, and gold chloride) which would be reduced in contact with excipients containing easily oxidisable organic substances.
Kieselguhr is used as an absorbent powder for volatile oils and solid substances which yield a solution when rubbed together, the mass being completed by the addition of hydrous wool fat, or liquid glucose, with powdered tragacanth or powdered gum acacia.
Liquid Glucose is specially suitable for the preparation of pills containing ferrous carbonate (see Liquid Glucose), and proves useful when syrup of glucose is insufficiently cohesive.
Liquorice Root in powder possesses excellent absorbent properties. By virtue of its fibrous nature powdered liquorice root forms an ideal vehicle in conjunction with a suitable cohesive excipient for massing hygroscopic substances or small quantities of soluble salts.
Milk Sugar is non-hygroscopic, and when powdered yields a gritty product, which forms a suitable vehicle for diluting alkaloids, alkaloidal salts, and potent substances generally, preparatory to their incorporation into masses by means of glycerin of tragacanth and syrup of glucose, or other suitable excipient. Powdered milk sugar is largely employed for the preparation of stock triturations.
Mucilage of Gum Acacia has been recommended as a suitable excipient for pills containing an appreciable quantity of aloes. Compound decoction of aloes or syrup of glucose is now more frequently used for the purpose. Pills prepared with mucilage of gum acacia are liable to harden excessively, or may become insoluble. For these reasons, syrup of glucose has practically replaced mucilage of gum acacia as a general excipient.
Soap is employed in the form of powdered hard soap or powdered curd soap. The trituration of about 25 per cent. of powdered curd soap with essential oils, when ordered in pills renders them more miscible with other ingredients, and less liable to subsequent separation from the mass. Powdered soap is used in eight of the official pill masses, and can be employed with advantage in conjunction with an absorbent powder or suitable liquid (as may be required) for massing substances, such as creosote, powdered camphor, or resins.
Syrup of Glucose forms a satisfactory general excipient for massing vegetable powders. When a gritty substance (such as reduced iron) forms an appreciable proportion of the material to be massed, the use of a small quantity of powdered gum acacia or powdered tragacanth in conjunction with the syrup is often advantageous, or liquid glucose may prove sufficiently cohesive.
Tragacanth in powder is valuable, if used sparingly, for increasing the cohesiveness of masses or for hardening purposes. Pills containing a small proportion of fibrous material, or composed of extracts, usually require the use of powdered tragacanth (about ¼ grain to each 5-grain pill) in conjunction with a suitable excipient, to prevent "pitting."
Wax, melted and added to the extent of about 10 per cent. to masses containing oils, hygroscopic, or very soluble substances, is not considered objectionable in cases where they are present in such quantity as otherwise renders impracticable their conversion into ordinary sized pills.
The rapidity with which pills produce effect when swallowed depends more upon the character of their mass than upon that of the coating with which they are enveloped. The selection of a suitable excipient is of primary importance. It has been shown by experiment that the presence of the coatings in general use does not retard the disintegration of pills (or exposure of their mass) to any appreciable extent. If a coating does not dissolve in contact with moisture and warmth, rupture readily ensues through expansion of the pill, providing the consistence of the latter is plastic and not unduly hard. The practice in vogue, in most pharmacies of invariably coating pills, unless otherwise ordered, is advantageous from every point of view. Coated pills are tasteless and elegant in appearance, they are less liable to deteriorate when kept, and are usually more acceptable to the patient than pills sent out enveloped in loose powder.
Sandarac Solution, diluted with about 25 per cent. of ether, is in general use for coating pills. Sandarac Solution, B.P.C., forms a convenient stock solution from which small bottles of the ethereal preparation can be readily prepared for use at the dispensing counter. About 5 to 8 drops of ethereal solution suffice to coat one dozen 5-grain pills. The pills should be shaken from the varnishing pot on to a slab previously smeared with a small quantity of almond oil. Pills coated with the ethereal solution are usually sufficiently dry to send out after ten minutes or a quarter of an hour. Pills coated with the alcoholic solution require a longer period. Pills containing large proportions of substances soluble in alcohol or ether are sometimes liable to adhere together if varnished; in such cases pearl coating is to be preferred. The appearance of pills containing white substances, which are generally massed with colourless excipients, is not usually improved by varnishing; in such instances pearl coating is also preferable.
Silver Leaf forms a convenient substance for coating pills which have a well-polished surface, free from powder, and which are firm in consistence. The quantity of liquid (usually diluted mucilage of gum acacia) used to render the pills adhesive, preparatory to enveloping them in silver leaf, must not be excessive, otherwise the appearance of the pills produced is dull and inelegant. Silver leaf should not be used for coating pills containing sulphides, or substances containing sulphurous compounds, unless they have been previously coated with varnish and dried. Pearl coating is preferable in such cases.
Gelatin Coating, although soluble, possesses no appreciable advantage over insoluble coatings such as silver leaf or varnish. The latter being brittle and non-elastic are rapidly ruptured by the swelling of the pill in contact with warmth and moisture. When applied by machinery adapted for the purpose gelatin coating yields elegant and satisfactory results. The process is carried out on a series of projections, upon which the pills are retained by suction. Piercing of the mass is avoided, and the coating of the pills is accomplished by dipping one half at a time in melted gelatin solution. In coating small batches the pills are impaled upon fine-pointed needles, and are dipped in thin melted gelatin solution (gelatin, 1, mucilage of gum acacia, 1, saturated solution of boric acid, to 10), rotated for a moment, and set aside to dry (preferably in a current of cool air). For batches of one or two dozen pills, iron wire (about No. 35 gauge) is sometimes employed instead of needles. The pills are impaled at each end of a 4-inch length of the wire, and when coated are dried by suspending each length of wire at its centre, in a current of cool air, care being taken to prevent the pills adhering.
Pearl Coating is extensively used as a coating for pills made by machinery. In comparison with sandarac and silver coatings, pearl coating is not often carried out at the dispensing counter. For certain purposes pearl coating possesses distinct advantages. Pills containing colourless substances, massed with colourless excipients, and substances possessing disagreeable odours, may often be pearl coated with advantage. Pills containing substances of sulphurous character which cannot be silvered unless previously varnished usually yield more elegant results when pearl coated. Pills containing substances which render the mass easily soluble in alcohol or ether, and those containing essential oils, are often covered with pearl coating in preference to varnish. Pearl coating usually consists of French chalk, adhering in a thin uniform layer and completely enveloping the surface of the pill. French chalk containing gluside 2 per cent. is sometimes used as a "sugar" coating. Elegant results depend to some extent upon practice, and more especially upon the application of a suitable amount of adhesive solution to the pill previous to coating. Preferably the consistence of the pills should be distinctly firm. The following method has proved satisfactory in practice:—Varnish the pills and transfer while still wet to a covered pot containing a small quantity of French chalk; rotate five or six times, and transfer the pills to a pill rounder; remove superfluous chalk by rotating and rubbing the pills on the rounder with demy paper; place a few drops (about 4 drops for each dozen 5-grain pills) of pill-coating mucilage (mucilage of gum acacia, 1, syrup, 1, distilled water, 4) in a dry covered pot; add the pills; rotate a few times, and transfer to another pot (concave within), containing a small quantity of French chalk; rotate gently and not too rapidly for about ten to fifteen seconds; transfer to an inverted lid, and rotate gently for a minute; set aside to dry for at least fifteen minutes, and finish by rotating the pills in a dry pot (concave within) until they have a uniform and polished appearance. The process, excluding the quarter of an hour during which the pills are set aside, usually occupies less than ten minutes if the requisite materials are ready to hand.
Sugar Coating can only be applied satisfactorily to large quantities of pills by machinery adapted for the purpose. When a sweetened pill coating is required at the dispensing counter it is customary to use French chalk containing 2 per cent. of gluside or a small percentage of sugar.
Keratin Coating is occasionally employed for covering pills which are intended to pass through the stomach and act in the intestines. Preferably the pills should be massed with a fatty excipient. They are then coated by dipping in melted cacao butter, and when dry are covered with two or three coatings of keratin solution. The results are rarely elegant, and it is doubtful if pills so treated serve the purpose intended.
Salol Coating is employed for the same purpose as keratin, and can be applied by rotating pills in melted salol. Experiments with pills coated with substances insoluble in solution of hydrochloric acid (0.2 per cent.) have demonstrated that such coatings are always ruptured in the presence of warmth and moisture, and it is therefore feasible to suppose that coatings of keratin and salol behave in a similar manner in the stomach.