The Strength of Fluid Extracts.
By JAMES W. MILL.
It has been proposed recently, in this journal and elsewhere, to reduce all fluid extracts to one uniform strength—that, viz., of eight troy ounces of drug to the pint, instead of sixteen troy ounces as is the rule now. In favor of this proposition it is urged that it is practically impossible to carry out the present formulas of the Pharmacopoeia for this class of preparations, the drug being directed in such very fine powder, and the expenditure of time and labor, necessary to secure a successful result, so great, to say nothing of the waste of alcohol, that dispensing pharmacists cannot, or, in fact, with only an occasional exception, do not prepare them themselves, but, instead, purchase the ready-made inferior products of the wholesale manufacturer. The reduction of the strength, as proposed, it is claimed, would obviate all trouble,—dispensing entirely with the application of heat, ensuring the complete exhaustion of the drug, and enabling the pharmacist to prepare his own fluid extracts in any quantity desired, and with very little trouble or expense,—a single percolation, to the extent of two pints for every sixteen troy ounces of drug, being all that would be necessary.
The writer fully realizes the great expenditure of time, labor and attention necessary to the correct preparation of fluid extracts of the present strength, and would gladly welcome any new process by which the desired object could be accomplished more easily. The proposed reduction of strength would, it is true, very materially lessen the labor, and render the preparation of a fluid extract a comparatively easy matter, but could such a preparation, with any propriety, be called a fluid extract? The term, "Fluid Extract," it is true, is purely arbitrary, and may be made to mean a fluid preparation, representing in every pint the medicinal virtues of sixteen, eight, or even four troy ounces of drug; but in a work like the Pharmacopoeia, claiming something of a scientific character, there surely should be as close a relation as possible between the language employed and the meaning intended to be conveyed. Now an "Extract," as defined by Wood and Bache in the U. S. D. (United States Dispensatory), is well understood to mean "a solid substance resulting from the evaporation of the solution of vegetable principles, obtained either by exposing the vegetable to the action of a solvent, or by expressing its juice in the recent state." Would not then the term "Fluid Extract" mean simply an extract-fluid, and very aptly characterize either the solid extract liquefied to a point at which it would be permanently fluid, or the original solution evaporated down to that point? Owing to the varying amount of soluble medicinal matter contained in different drugs, fluid extracts made on this plan would, as a class, be very various in strength,—a given quantity of one fluid extract representing one proportion of drug, another a different proportion,—practically, therefore, so great concentration is not desirable, and some standard is necessary which includes uniformity of strength and facility of preparation, as well as adaptability to the wants of the physician. The present standard of sixteen troy ounces to the pint seems best to fulfil these requirements. Made of this strength, a fluid extract of a drug is its fluid representative, to all medicinal intents and purposes, the same thing as the drug itself—superior to it, in fact, in having a more prompt therapeutic action and readier facility of administration. What more desirable preparation of a crude drug could be offered the medical profession or their suffering patients?
But—and this is the main question—are fluid extracts of this strength practicable? Is their correct preparation within the range of the usual facilities of a dispensing establishment? Or does it involve so great an expenditure of time and labor, and so great an outlay for costly apparatus, that the already much pre-occupied pharmacist may justly excuse himself from the undertaking? While protesting against any change in the strength of fluid extracts, the writer does not endorse the formulas given by the Pharmacopoeia for their preparation. Indeed, literally construed, they are impracticable. It is practically impossible, with the usual facilities to be found in stores,—even the best appointed,—to reduce a drug to the degree of fineness directed by the Pharmacopoeia. For example, in the process for fluid extract of buchu, the drug is directed to be in powder "moderately fine," i. e., a powder that will pass through a sieve of fifty meshes to the inch. Now it is simply not possible to accomplish this within any reasonable time, or when any but the smallest quantities are operated on. In the experience of the writer it requires considerable muscular exertion to obtain even one-third of any given quantity (over a few ounces) in the state of fineness directed. The only practicable thing is to grind the drug as fine as possible, and sift it successively through sieves twenty, forty, and sixty meshes to the inch,—repeating the operation two or three times, or so long a any fine powder is obtained. In packing for percolation the powder are arranged in the order of their fineness, commencing with the finest—thus exposing the least permeable portions of the drug to the most solvent portions of the menstruum, and also ensuring a slow rate of percolation, so essential to a successful result. Operating in this way, perhaps a little more menstruum is required than if the drug were in "moderately fine" powder, as directed, but then the process is brought within the range of practicability, while before it was not.
The low degree of temperature directed for the evaporation of the percolate furnishes another ground for reasonable objection to the officinal processes, on account of the waste of alcohol, the temperature specified not permitting of its recovery by distillation. Economically considered, and on the scale of the Pharmacopoeia, this objection hardly has any weight, as the waste would be but trifling; on any larger scale, however, the saving of the alcohol becomes a matter of some economical importance, and its recovery therefore, by distillation in a water bath still, should receive the sanction of the Pharmacopoeia. No appreciable injury to the medicinal matter can result from the necessary increase of temperature, as this would be more than counterbalanced by the more perfect exclusion of atmospheric influences.
With these modifications of the formulas surely the preparation of fluid extracts, of the strength of sixteen troy ounces of drug to the pint, is not a very difficult matter. The apparatus required is exceedingly simple, a drug mill, a set of sieves, a percolator, and a water bath still being all that is necessary. Is there a druggist in the land who considers his vocation anything more than the mere buying and selling of drugs, not already possessed of these necessary implements of his art? Scientifically considered a simple matter, the correct preparation of a fluid extract does involve strict care and attention, and a conscientious selection of the crude material. No amount of science will atone for poor material or careless manipulation.
The proposed reduction of strength, it is claimed, would ensure the complete exhaustion of the drug. In a limited number of instances, doubtless, this claim would hold good,—in drugs, for example, like ginger, which yield their medicinal matter easily and readily to a solvent; but that senna, rhubarb, cinchona, or drugs generally, can be exhausted in this way, is altogether contrary to the writer's experience. Just the amount of menstruum necessary for exhaustion varies, of course, with the varying amount of soluble medicinal matter contained in different drugs; but, as a rule, adapted to the treatment of drugs generally on the small scale, and in an ordinary displacement funnel, three pints of percolate for every sixteen troy ounces of drug, although excessive in some cases, no doubt is yet the safest for general use. Were the percolation stopped at two pints of percolate for every sixteen ounces of drug, the resulting preparation would, in most cases, be simply a concentrated tincture, representing no definite quantity of drug,—superior, perhaps, to many of the so-called fluid extracts of the market, but by no means to be considered a true representative of the original drug. Doubtless there are physicians to whom the excess of alcohol would not be an objectionable feature, and who would prefer such concentrated tinctures, prepared by the apothecary himself, to the uncertain products of the market. It might be well enough therefore (although the writer does not recommend it), to introduce them into the Pharmacopoeia, under, however, a separate and distinct title, such as Tincturae Fortiores, retaining Extracta Fluida for the many physicians who dislike to prescribe alcohol, except in minimum doses.
The following formulas illustrate the ideas of the writer on this subject
Extractum Buchu Fluidum.
|Take of||Buchu,||sixteen troy ounces.|
|Glycerin,||four fluid ounces.|
|Alcohol and Water,||sufficient.|
Grind the buchu, and sift it successively through No. 20, No. 40, and No. 60 sieves, keeping the result of each sifting separate. Mix the glycerin with twenty fluid ounces of the alcohol, and with five fluid ounces of this menstruum moisten the different lots, and introduce them successively into the percolator, commencing with the finest; pack firmly, and gradually pour on the remainder of the alcohol and glycerin, following it with a mixture of alcohol and water in the same proportion, till the drug ceases to absorb any more and the menstruum remains permanently on the surface; then, having closed the orifice of the percolator with a cork and put on the cover, set aside to macerate. At the end of twenty four hours, or longer, remove the cork and allow the percolation (which should not be faster than ten drops per minute) to proceed. When the liquid has disappeared from the surface pour on menstruum till twelve fluid ounces of percolate have passed; set this portion aside, and continue the percolation with the remainder of the menstruum, and finally water, till the buchu is exhausted, or until two pints more of percolate have been obtained. Concentrate this by distillation in a water-bath still till reduced to four fluid ounces, and mix it with the reserved percolate. Allow the mixture to stand for twenty-four hours and filter through paper.
The menstruum employed in this formula is less alcoholic than the Pharmacopoeia directs, but it is sufficiently so to extract and retain in solution the active principles of buchu. The glycerin seems to prevent the separation of resinous matter, which occurs during distillation, when a purely alcoholic menstruum is employed. In the unfiltered fluid extract no deposit had occurred after the lapse of several weeks.
In connection with this fluid extract the following observations may be of some interest: Thirty-two troy ounces of buchu were prepared in the manner above described, and packed in a percolator six feet high and two inches wide at the mouth, gradually tapering to one and a quarter inches at the bottom. A full supply of menstruum (alcohol three parts, water one part, sp. gr. .895) was poured on at the beginning, and percolation commenced on the second day after at the rate of about ten drops a minute. The percolate was received in a small flask, in nine separate portions, each measuring seven and a half fluid ounces. The first portion was received about twenty-four hours after the commencement of percolation, and the remaining portions at intervals of about the same length. They had the sp. gr. Respectively of .995, .985, .965, .960, .950, .935, .920, .910, .900. A mixture of the first four portions, with sufficient of the fifth added to make the measure up to thirty-two fluid ounces, had the sp. gr. .965. A parallel experiment, conducted in an ordinary cylindrical glass percolator, three and a half inches in diameter, and fifteen inches high, showed the same ultimate result, but not so great concentration in the first portions of percolate—the sp. gr. of the first thirty-two fluid ounces being .960 instead of .965 as in the other experiment. The last portion of percolate had a very light color, and but little of the odor or taste of buchu, and the drug may safely be considered exhausted at that point. All drugs, however, are not so readily exhausted as buchu; and although, in this case, thirty-two fluid ounces of percolate would very well represent sixteen troy ounces of drug, it does not follow that it would be a safe rule in all cases; it is only prudent therefore that the Pharmacopoeia should direct a little too much menstruum in some instances than not enough in others.
Extractum Cinchonae Fluidum.
|Take of||Cinchona, yellow,||sixteen troy ounces.|
|Glycerin,||eight fluid ounces.|
Grind and sift the cinchona in the same manner as directed for buchu, mix the glycerin with three pints of the alcohol, and with six fluid ounces of this menstruum moisten the cinchona, and pack moderately in a glass percolator; pour on the balance of the alcohol and glycerin, and then the remaining pint of alcohol, following it with water, till about four pints of percolate have been obtained. Put the percolate into a water-bath still and distill off the alcohol till reduced to the measure of sixteen fluid ounces. This is essentially the formula recommended by Dr. Squibb (Amer. Jour. Phar., vol. 39, page 515), differing only in this, that the glycerin forms part of the menstruum—thus securing its solvent as well as its preservative influence, and also reducing, to the extent of the quantity of glycerin present, the amount of evaporation necessary. With the glycerin diluted to extent it is in this formula the percolation is not too tedious.
Extractum Hyoscyami Fluidum.
|Take of||Henbane Leaf,||sixteen troy ounces.|
|Glycerin,||four fluid ounces.|
|Alcohol and Water,||each a sufficient quantity.|
Mix the glycerin with twelve fluid ounces of alcohol and eight fluid ounces of water, and with six fluid ounces of this menstruum moisten the henbane previously prepared for percolation. Pack firmly in a cylindrical glass percolator, and pour on menstruum till the surface remains covered; macerate for twenty-four hours, then proceed with. the percolation, using the remainder of the glycerin menstruum, dilute alcohol and water successively till at least three pints of percolate have been obtained. Of this reserve the first twelve fluid ounces, and distill the remainder in a water-bath still till reduced to eight fluid ounces; to this add the reserve percolate, and continue the distillation till reduced to such a point that, when cold, the finished fluid extract shall measure exactly sixteen fluid ounces.
In the same way prepare fluid extract of senna, uva ursi, spigelia, sarsaparilla, dulcamara, serpentaria, taraxacum, and gentian.
Extractum Rhei Fluidum.
|Take of||Rhubarb,||sixteen troy ounces.|
|Diluted Alcohol,||each a sufficient quantity.|
|Glycerin,||four fluid ounces.|
Mix two fluid ounces of the glycerin with fourteen fluid ounces of alcohol, and with six fluid ounces of this moisten the rhubarb (ground, and as much as possible of it passed through a No. 40 sieve). Pack moderately in a conical glass percolator, and pour on the remainder of the glycerin and alcohol. Macerate for twenty-four hours, then mix the remaining two fluid ounces of glycerin with one pint of alcohol and fourteen fluid ounces of water, and with this and diluted alcohol continue the percolation till first sixteen fluid ounces, which reserve, and then about two pints more of percolate have been received; this latter percolate distill in a water-bath still till reduced to twelve fluid ounces, to this add the reserve percolate, and continue the distillation till reduced to such a point that, when cold, the fluid extract shall measure exactly sixteen fluid ounces.
Carefully prepared in this way, from really good material, fluid extracts are very faithful representatives of the original drugs, and their preparation is not more difficult than is that of compound syrup of sarsaparilla, for example, or any other preparation requiring care and attention. Aside from the satisfaction of knowing just what he is dispensing, the preparation of fluid extracts by the apothecary further recommends itself on economical grounds, for by the saying of the alcohol and by taking the precaution to prepare a season's supply during the winter,—when there is more leisure time, and when the same fire can be used that is used for heating purposes,—their cost can be brought considerably below the price paid to the wholesale manufacturer.
Chicago, Ill., August, 1870.
—The Pharmacist, Chicago, Oct. 1870.
[NOTE.—We cannot withhold a hearty approval of the views offered in the paper of Mr. Mill in favor of retaining the officinal strength of fluid extracts, and of the manner of executing the processes. The constant complaint amongst apothecaries of the present day in regard to the labor of comminuting drugs seems to indicate a growing contempt for the mortar and handmill as proper pharmaceutical implements. There has also grown up in the pharmaceutic mind a remarkable dread of the effects of heat, be it ever so moderate, on the medicinal power of drugs. It is admitted at once that direct heat has a tendency to injure all solutions of organic matter; but when the water bath (or water bath still) are employed, they embody every requisite, except in case of very volatile substances, as the temperature of the former may be regulated when necessary as low as 120° Fahr., and the latter never exceeds 212° Fahr.; but even these are laid under ban by some of the writers of the later times. Some of these reforms are certainly to be deprecated as a decline in the practice of our art, and while we shall hail the advent of any process which shall really substitute evaporation in fluid extracts, we believe a more serious attention on the part of the fathers in pharmacy to the improvement of the means of comminution in the apothecary's shop will result in real progress in the art of extracting drugs.—EDITOR AM. JOUR. PHARM.]