Teintures (Alcooliques) Alcooles, Fr.; Tinkturen, G.; Tinture alcooliche, It.; Tinturas alcoholicas, Sp.
Tinctures, in the pharmaceutical sense of the term, are alcoholic solutions of medicinal substances, prepared by maceration, digestion, or percolation. Solutions in spirit of ammonia and ethereal spirit are embraced under the same denomination, but are severally distinguished by the titles of ammoniated tinctures and ethereal tinctures. The advantages of alcohol as a menstruum are that it dissolves principles which are sparingly, or not at all, soluble in water, and contributes to their preservation. when dissolved, while it leaves behind some inert substances which are dissolved by water. In no instance, however, is dehydrated alcohol employed. Because of the slight amount of water in it, official alcohol dissolves more or less of substances which are insoluble in dehydrated alcohol, while its solvent power in relation to bodies soluble in that fluid is sufficient for all practical purposes. Diluted alcohol or proof spirit is often preferable to official alcohol, as it is capable of extracting a larger proportion of those active principles of plants which require an aqueous menstruum, while at the same time it is strong enough to prevent spontaneous decomposition, and has the advantages of being cheaper and less stimulating, although a few tinctures when prepared with weak alcoholic menstrua undergo some deterioration in time, in consequence of acetous fermentation taking place in the alcoholic fluid. The best preventive is to keep them in full and well-closed bottles, at a low temperature. The diluted alcohol of the different Pharmacopoeias is not of the same strength; that of the United States consists of equal volumes of official alcohol and water, and has the sp. gr. of about 0.936 at 15.56 C. (60° F.), while the British has four official diluted alcohols—70, 60, 45, and 20 per cent. Alcohol, or rectified spirit, is preferred as a solvent when the substance to be extracted or dissolved is nearly or quite insoluble in water, as in the instances of resins, guaiac, camphor, and the essential oils. The presence of water is here injurious, not only by diluting the menstruum, but also by exercising an affinity for the alcohol which interferes with its solvent power. Thus, water added to an alcoholic solution of one of these bodies produces a precipitate by abstracting the alcohol from it. Diluted alcohol, or proof spirit, is employed when the substance is a soluble both in alcohol and in water; or when one or more of the ingredients are soluble in the one fluid and one or more in the other, as in the case of vegetable bodies which contain extractive or tannin, or the natural salts of the alkaloids, or gum united with resin or volatile oil. As these include the greater number of medicine's from which tinctures are prepared, diluted alcohol is most frequently used. In the preparation of the tinctures, the drug should be dry, and properly comminuted by being bruised, sliced, or pulverized. It is usually better in a moderately fine than in a very fine powder; the proper degree depends, however, upon the ease with which the menstruum extracts the soluble principles. The recommendations of the International Protocol included the use of 70 per cent. alcohol for the various tinctures, but as this has not proven to be the best menstruum for some drugs, the U. S. P. has not always followed the suggestion.
In the U. S. P. IX the general article on tinctures is as follows:
"Tinctures are alcoholic preparations made by extracting the valuable principles from drugs by the use of appropriate menstrua or solvents. Tincture of ferric chloride and tincture of iodine are exceptional, not being made by extraction; they are alcoholic solutions of chemical substances. Tinctures of potent drugs are made of the strength of ten grammes [or 154 grains] of drug in one hundred mils [or 3 fluidounces, 183 minims 1 of tincture. The other tinctures vary in the proportion of drug in the finished tincture. Tinctures are made by percolation with few exceptions. Maceration or solution is preferred when from its physical character the drug is not suitable for percolation. The majority of official tinctures are prepared under one or the other of the two type processes described, and in each formula directions are given as to the process to be followed with such modifications as may be necessary. A number of drugs require special manipulation for the preparation of satisfactory tinctures, and for these the formulas in full will be found in the text. Where it has been found possible and desirable to standardize the tinctures a rubric and assay have been added. Tinctures should be stored in tightly-stoppered bottles, kept in a cool place, and protected from light.
Type Process P—Percolation.
"Moisten the powdered drug or mixed drugs designated in the formula with a sufficient quantity of the prescribed menstruum to render it evenly and distinctly damp, transfer it to a percolator, and, without pressing the powder, allow it to stand well-covered for six hours; then pack it firmly, unless otherwise directed, and pour on enough of the menstruum to saturate the powder and leave a stratum above it. When the liquid begins to drop from the percolator, close the lower orifice, and, having closely covered the percolator, macerate for twenty-four hours. Then allow the percolation to proceed slowly, gradually adding sufficient of the menstruum to make one thousand mils [or 33 fluidounces, 6 ½ fluidrachms] of finished tincture.
"Modification for Assayed Tinctures.—In Tinctures that are directed to be assayed, allow the percolation to proceed until the percolate measures nine hundred and fifty mils [or 32 fluidounces, 59 minims]. Assay a sample of this percolate as directed and from the alka-loidal content thus determined, ascertain by calculation the amount of alkaloids in the remainder of the liquid and add to this enough of the menstruum to make the finished Tincture conform to the required alkaloidal standard.
Type Process M—Maceration.
"Macerate the drug or mixed drugs designated in the formula in a stoppered container, in a moderately warm place, with seven hundred and fifty mils [or 25 fluidounces, 173 minims] of the prescribed solvent (unless a different amount is specified in the formula). Continue the maceration with frequent agitation during three days or until the drug is practically extracted, transfer the mixture to a filter and, when the liquid has drained off completely, gradually wash the residue on the filter with enough of the solvent to make one thousand mils [or 33 fluidounces, 6 ½ fluidrachms] of finished tincture." U. S.
The British Pharmacopoeia in the Appendix IX. (see Part III) has provided detailed instruction for both percolation and maceration processes.
Tinctures were at one time universally prepared by maceration or digestion. Our own Pharmacopoeia formerly directed maceration at ordinary temperatures, and extended the period to two weeks. In several instances in which maceration is ordered in the U. S. Pharmacopoeia, maceration for three days is directed, but the Br. process requires seven days. When circumstances require that the tincture should be speedily prepared, digestion may be resorted to. Care should always be taken to keep the vessels well stoppered, in order to prevent the evaporation of the alcohol. The materials should be frequently shaken during the digestion or maceration, and this caution is especially necessary when the substance acted on is in the state of powder. The tincture should not be used until the maceration is completed, when it should be separated from the dregs either by simply filtering it through paper, or, when force is requisite, by expressing it through linen, and filtering.
The plan of preparing tinctures by percolation has been extensively adopted, and has been found to answer well when skilfully executed. In the present edition of our Pharmacopoeia, percolation has been adopted as the rule, maceration being directed in some instances in which it was deemed preferable. The method of making tinctures by diluting fluidextracts, except in a few special cases, is not to be recommended. The menstruum directed for the fluidextract is most frequently not identical with that used for the tincture, and precipitation of active constituents often ensues when this easy method is employed. Owing to the larger dose of the tinctures, and consequently less degree of concentration, a larger proportion of water can be used in their menstrua than in fluidextracts, and this is a distinct advantage, as tinctures are frequently prescribed in combination with aqueous solutions.
Another mode of exhausting medicines by spirit has been proposed by H. Burton. It consists in suspending in the solvent, immediately under its surface, the solid matter contained loosely in a bag. The liquid in contact with the bag, becoming heavier by impregnation with the matters dissolved, sinks to the bottom; its place is supplied with a fresh portion, which in its turn sinks, and thus a current is established, which continues until the solid substance is exhausted or the liquid saturated. During the maceration the bag should be occasionally raised above the surface of the liquor in the bottle, allowed to drain, and then again immersed. It is asserted that the period of maceration is much shortened in this way. For this mode of preparing tinctures Samuel Gale has proposed the use of a cylindrical stoneware vessel with a diaphragm capable of being supported at different heights by projections from the inner surface of the jar, with corresponding notches in the diaphragm, to permit its easy passage to the lower ledges. The material is to be placed upon the diaphragm and kept covered with the menstruum.
Tinctures prepared by adding alcohol to the expressed juices of plants have been long in use on the continent of Europe, and have been brought into notice in Great Britain. They are sometimes called in England preserved vegetable juices. This method of preparing tinctures has, however, been abandoned by both the U S. and Br. Pharmacopoeias. Preserved juices are often energetic, yet it is obvious that tinctures prepared from the fresh plant must be still more so, as they contain necessarily not only the soluble active matter of the juice, but also that which, when the juice is expressed, is left in the solid residue of the plant. For further information see U. S. D., 19th ed., p. 1293.
A process for making tinctures from fresh drugs was official in the U. S. P. VIII. It was deleted from the U. S. P. IX, but introduced into the National Formulary IV under the heading Tincturae Medicamentorum Recentium as follows :
"Tinctures of fresh drugs, when not otherwise directed, are to be prepared according to the following general formula: The Fresh Drug, cut, bruised, or crushed, five hundred grammes [or 17 ounces av., 279 grains]; Alcohol, one thousand mils [or 33 fluidounces, 6 ½ fluidrachms]. Macerate the drug with the alcohol in a closed vessel in a moderately warm place during fourteen days, with occasional stirring; then strongly express the liquid and filter it through paper." N. F.
Tinctures should be kept in bottles accurately stoppered, in order to prevent evaporation, which might in some instances be attended with serious inconvenience, by increasing their strength beyond the official standard.
Medicines which act in small doses are most conveniently administered in tinctures, as the proportion of alcohol in which they are dissolved is insufficient to produce an appreciable effect. Those which must be given in large doses should be cautiously employed in this form, lest the injury done by the menstruum should more than counterbalance their beneficial operation. This remark is particularly applicable to chronic cases, in which the use of tinctures is apt to lead to the formation of habits of intemperance. The tinctures of the weaker medicines are more frequently given as adjuvants of other remedies than with the view of obtaining their own full effects upon the system.
In the revision of the Pharmacopoeia of 1890, wherever practicable, the proportion of drug to finished tincture was made either 20, 15, 10, or 5 Gm. per 100 mils. Progressive pharmacy demands greater uniformity and simplicity in the processes, and hence in the II. S. P. VIII and IX practically all of the tinctures have been brought into two classes, 20 and 10 Gm. of drug per 100 mils. The potent tinctures, which contained mainly 15 Gm. of drug per 100 mils in the U. S. P. 1890, were reduced to 10 Gm. per 100 mils in 'order to comply with the recommendations of the Brussels Conference of 1902 for the unification of the strength of Potent Remedies.
A tabulated comparison of the tinctures of the P. G. IV and P. G. V as to sp. gr., extractive percentage and alkaloidal content, is available for those to whom it would be of value in the Yearbook of the A. Ph. A., 1913, p. 84.