This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
5. Decoctions (decocla) differ from infusions simply in the circumstance that boiling is used in preparing them. They are liable to the same objections as the hot infusions in a still greater degree, but are convenient when haste is requisite, and the active principles of the medicine are not likely to be materially injured by the heat. As atmospheric air, at a high temperature, is liable to act injuriously on various vegetable principles, the process should be performed in a covered vessel, and should not be continued longer than is necessary to the end in view. Hard, tough, fibrous substances are often most conveniently treated in this way; but the process is altogether inapplicable to those medicines whose activity depends upon a volatile principle, as, for example, upon a volatile oil. In the present Pharmacopoeia, a somewhat modified plan of preparing the decoctions has been adopted. The substance treated is boiled with water generally for fifteen minutes; after which the whole is placed upon a strainer, and sufficient water added, through the strainer. to make the decoction measure a certain quantity, which is generally a pint. More precision in the result is thus obtained than by the old method of merely boiling and straining.
6. Tinctures (tinclurae) are alcoholic solutions of medicinal principles. As, in consequence of the preservative influence of the alcohol, they may generally be kept, in well-closed bottles, an indefinite length of time, they are almost always prepared by the pharmaceutist, and very seldom externporaneously. In much the larger proportion of them, the process of percolation is employed, somewhat varied according to the nature of the medicine used. It should be remembered that some of them are prepared with officinal alcohol (sp. gr. 835), and others with diluted alcohol, made by mixing equal measures of the officinal alcohol and water. The former are of course more stimulating than the latter, so far as concerns the menstruum; and this circumstance may be occasionally of practical importance. The officinal tinctures (U. S. Pharmacopoeia) of the pure resins, gum-resins, balsams, aconite root, hemp, nux vomica, American hellebore, ginger, castor, and iodine are made with the stronger alcohol; almost all others, including those of the roots, barks, leaves, and fruits of plants, with the diluted. This set of preparations is applicable only when some degree of stimulation is admissible, or when the active principle dissolved in the alcohol is so powerful as to render the amount of the menstruum employed in each dose insignificant, as in the instances of tinctures of aconite root and opium. They are especially useful as adjuvants to other forms of preparation, when it is desirable to render these somewhat more stimulating. Thus, tincture of Peruvian bark may, in low forms of disease, be very appropriately added to the infusion or decoction, or to the solution of sulphate of quinia. In relation to the long-continued employment of tinctures, the practitioner should be aware of the danger of establishing a habit of intemperance, and should be on his guard accordingly. The resinous and camphorous tinctures become turbid on the addition of water, in consequence of the precipitation of the resin or camphor, and should therefore be given with a viscid liquid. as mucilage, syrup, or sometimes milk, or, if diluted with water alone, should be taken immediately after admixture.
7. Spirits (spirilus) are closely analogous to tinctures, being, like them, solutions of medicinal principles in alcohol, but differing, as formerly understood, in being prepared by distillation. As many of the spirits are now prepared by simply dissolving in alcohol the principles originally separated from the substances containing them by distillation, and as this mode of preparation is recognized in the present U. S. Pharmacopoeia, the meaning of the term must be considered as having been officially extended so as to include all alcoholic solutions of volatile principles, whether made by means of distillation or otherwise. Thus, the term spirit of peppermint, originally applied to the liquid obtained by distilling peppermint with alcohol, is now used to designate the simple alcoholic solution of the volatile oil, which in the previous Pharmacopoeia was denominated tincture of oil of peppermint.
8. Wines (vina) differ from the tinctures simply in being prepared with wine as the menstruum, instead of alcohol or diluted alcohol. These are also usually the subjects of officinal preparation. The advantages of wine, in the cases to which it is applicable, are that it is less stimulant than alcohol, while it is more effectual than water in counteracting: the tendency of the orgauic medicinal principles to decomposition, and. in consequence of the alcohol it contains, is sometimes more effective as a solvent For the purposes of a medicinal solvent, the stronger wines are preferred to the weaker; as the latter are apt to contain principles incompatible with the substance dissolved. Thus, Madeira, sherry, or Teneriffe should be preferred to claret or the Rhine wines. Port wine is seldom proper, on account of the tendency of the tannic acid it contains to form insoluble compounds with other bodies.
9. Vinegars (aceta) are simply infusions made with cold distilled vinegar, or diluted acetic acid. Very few of them are used; and these more in the preparation of other forms of medicine, than for direct administration. Thus, vinegar of squill is much used as an ingredient in the syrup of squill, seldom alone. This class of preparations is based on the fact, that in certain cases acetic acid favours the solvent property of water, while it also has a preservative effect, though in this respect much less efficient than alcohol.
10. Syrups (syrupi) are aqueous solutions of sugar impregnated with medicinal principles. When the term syrup (syrupus) is used singly, it implies, officinally, a simple solution of sugar in water, of a certain recognized strength, which, according to the U. S. Pharmacopoeia, is about two and a half pounds of sugar to a pint of water. The medicated syrups are designated by the name of their chief medicinal ingredient, as syrup or rhubarb, syrup of ginger, etc. The mode in which the medicinal impregnation is effected varies much with the character of the medicine. The syrups are generally subjects of officinal direction, and are kept ready made in the shops. Their advantages are that the sugar serves to cover the disagreeable taste of the medicine, and at the same time prevents its spontaneous decomposition. They are favourite prepara-tions in infantile cases; but, in their use, the physician should bear in mind the frequently injurious effect of much sugar in a feeble stomach.
11. Honeys (mellita) differ from the syrups only in the substitution of honey for sugar. They are at present little used; honey, in consequence of its impurities, being inferior to sugar as a preservative.
12. Oxymels are preparations in which the menstruum consists of honey and vinegar combined. They are now almost out of use; oxymel of squill, which for some time was the only one officinal, having been recently discarded by the Pharmacopoeias
13. Fluid Extracts (extracta fluida) are highly concentrated solutions of the active constituents of medicines, or the active constituents themselves extracted in the liquid state: and are often very convenient and efficient preparations. They have been introduced into use at a comparatively recent date, and are at present much employed. There are two kinds of them. In one. the active principles of the medicine are extracted by alcohol or diluted alcohol, sugar is often added as a preservative, and to improve the flavour, and the alcohol is afterwards to a greater or less extent evaporated. These are concentrated alcoholic solutions, or aqueous solutions with a little alcohol remaining;. The other kind consist mainly of volatile oil and resinous matter, extracted by ether from the medicine, and subsequently freed from the solvent by evaporation. To the latter division the name of Oleoresins (oleore-sinae), expressive of their composition, has been applied in the latest edition of our Pharmacopoeia.
14. Glycerates (Glycerols) are preparations, recently introduced. in which glycerin serves as the menstruum. Advantages of these preparations are that glycerin dissolves substances which water will not, that it does not evaporate spontaneously like water and alcohol, and that it contributes to the preservation of the substance dissolved, without being stimulating or irritating like spirit. Several of the glycerates are more or less used, as those of iodine, aloes, and tar; but they do not as yet form a class in our officinal code.
15. Spray. As it is desirable, in certain diseases of the air-passages, to bring various substances into contact with the diseased surface in the liquid form; but, from the great sensitiveness of the respiratory organs, it has been found extremely inconvenient to introduce liquids in an aggregate condition beyond the glottis; the expedient has been adopted of bringing the liquid into a state of extremely minute division, and then causing it to be inhaled admixed in this condition with the atmospheric air. The names of atomization, pulverization, and nebuliza-tion have been given to the different processes by which this minute division is effected; and instruments adapted to the purpose are called atomizers, pulverizers, etc. In treating of the forms in which liquids are used, it was necessary to call attention to this method of applying them; but it will be found more convenient to consider the subject fully in con-nection with the lungs, as one of the parts to Which medicines are applied; and the reader is accordingly referred to the subsection in which inhalation is treated of.