Extemporaneous Prescriptions are formulae written by the physician on the instant (ex tempore), to meet the requirements of individual cases.
A prescription should begin with the name of the person for whom it is designed, and the date on which it is written. Then follows the Latin word Recipe, usually abbreviated by the sign Rx, and signifying "Take," or "Take thou;" next the names and quantities of the ingredient to be used, which are also expressed in Latin; then the directions to the compounder, followed by the directions to the patient, the last being now usually expressed in English and finally the signature of the prescriber.
A prescription then has four component parts, viz.:—
SUPERSCRIPTION,—which consists of the name of the party for whom it is designed, the date, and the sign Rx—signifying "Take thou."
- INSCRIPTION,—the body of the prescription, consisting of one or more of the following subdivisions, viz.—the
- Basis,—or chief ingredient
- Adjuvant,—to assist the action of the basis.
- Corrective,—to correct some injurious quality of the other ingredients.
- Vehicle or excipient,—to give it a suitable form.
SUBSCRIPTION,—the directions for the compounder, usually expressed in contracted Latin.
SIGNATURE,—the instructions for the administration of the medicine, in English or Latin, followed by the signature of the prescriber.
A prescription may, however, contain the basis alone, or the basis with the adjuvant, or the basis with a simple vehicle or diluent. A single ingredient may serve a double or a treble office, as the Aromatic Syrup of Rhubarb with Quinine, in which the syrup serves as an adjuvant to increase the action of the quinine, as an excipient to cover the taste, and as a vehicle to facilitate the administration of the dose directed. Again, the basis may need no aid in doing its work, and may require no corrective of its action, nor any special vehicle. On the other hand, there is no limit to the number of ingredients that may be used, provided that the prescriber has a clear idea of something to be accomplished by each one, and also provided that there is no chemical or medicinal incompatibility between them. Formerly prescriptions were very complex, and contained a great many curious and incongruous ingredients. As Dr. Phillips well says, "the tendency of the present age is toward mono- rather than poly-pharmacy, and prescriptions with the orthodox adjuvans and corrigens are less frequently seen than formerly." There is danger, however, in carrying this simplicity too far, for there is no doubt but that proper combinations of medicines will often produce effects for the patient's good, which could not be obtained from the use of any one remedy.
Procedure in Writing a Prescription. The first step is to write the name of the patient, the date, and the sign Rx. Then the title of each ingredient should be written in Latin and in the genitive case, except when only a certain number of an ingredient is to be used the ingredient should be in the accusative case, as for example, "Vitellum unum,—one Yolk-of-egg."
Next the quantity of each ingredient sufficient for one dose should be mentally determined, and multiplied by the number of doses which the mixture, etc., is to contain, and the result set down in signs and Roman numerals opposite the designation of each article. Directions to the pharmaceutist and for the patient being added, and the prescriber's name or initials being affixed, the prescription is completed. Frequently, the ingredients and their quantities for but one dose, in pill, powder, suppository, etc., are named, with instructions to make a certain number after the formula prescribed. When an unusually large dose of any poisonous drug is prescribed, it is customary to underline the quantity, so as to call the attention of the compounder to the fact that the large dose is ordered intentionally.
An Example will perhaps make the foregoing more comprehensible, and at the same time serve to indicate the style of writing usually employed. The following formula is that ordered in the U. S. Pharmacopoeia for the preparation known as "Black Draught," but officially styled the Compound Infusion of Senna; approximate weights and measures being substituted for the pharmacopoeial metric weights.
|For Mrs. Gray.
|July 7th, 1894.||| SUPERSCRIPTION.
|(Basis).||| Sennae, semiunciam,||| INSCRIPTION.|
|| .||Of Senna, half an ounce,||||
|| Magnesii Sulphatis,||||
||||Of Magnesium Sulphate,||||
|(Adjuvant.)||| Mannae, and unciam unam,||||
||||Manna, of each an ounce,||||
|(Corrective.)||| Foeniculi, drachmam unam,||||
||||Of Fennel, one drachm,||||
|(Vehicle.)||| Aquae Bullientis fluiduncias octo,||||
||||Of Boiling Water, eight fluid-ounces.||||
|Macera per horam in vase clause, deinde cola.
Macerate for an hour in a closed vessel, then strain.
|Signa,—Mark or Write, thus—A wineglassful every four hours 'till it operates.||| SIGNATURE.|
|T. F. Wood, M. D.||||
Abbreviated in the style usual among physicians, the above prescription would read as follows, viz.:
|For Mrs. Gray.||July 7th, 1894.|
|Mac. per hor. in vase clauso, deinde cola.|
|Sig.—A wineglassful every four hours, 'till it operates.
As the result of the above is nearly identical with the official preparation, we might write the same prescription more simply, as follows,—
Rx. Infusi Sennae Compos., ℥viij,
with the proper superscription and signature; this being the manner of prescribing the official preparations.
It will be noticed that in the above analysis the term "basis" covers two ingredients; but it is obvious that either of them might be considered the principal agent, and the other one classed as an adjuvant.
"These four parts of a formula are intended to accomplish the object of Asclepiades, curare cito, tute et jucunde; in other words, to enable the basis to cure quickly, safely and pleasantly." (Pareira.)
Another Example will illustrate the mental operations which should always be followed by a prescriber; for no matter how good a memory he may have, lie will surely make a grievous mistake some day if he follow the practice of writing prescriptions from memory. Furthermore, the unscientific character of the latter habit will, when appreciated, prevent any educated physician from indulging in it. Every prescription should be written with a definite purpose in view, consequently the mind of the prescriber should weigh each step carefully, and should avoid all slavish subjection to ready-made formulae. Suppose, then, that we wish to order for Miss Graham an emulsion of Castor Oil, flavored and sweetened so as to make it less disagreeable to the taste than it naturally is. If the ingredients were simply mixed together, as in the previous example, the result would be an unsightly preparation, consisting of sweetened and flavored water with the oil floating on top. So we require that the process of emulsification be first accomplished, by which the oil is minutely subdivided and suspended in the water, by the aid of the emulsifier, which may be any viscid excipient, as gum, soap, or yolk-of-egg. Taking the last-named for the emulsifying agent, we would begin by writing down in order the following terms, as stated in italics, viz.:—
|For Miss Graham.||June 10th, 1894.|
|Olei Ricini, (of Oil of Castor),
|Tere bene simul: dein adde—(Rub well together; then add—)|
Having gone so far, we begin to think of an agreeable vehicle, and choosing from the many Syrups at our disposal that of Ginger, and from the flavored Waters that of Cinnamon, we write further for these as the ingredients to be added, thus:—
- Syrupi Zingiberis, (of Syrup of Ginger),
Aqua Cinnamomi, (of Cinnamon-Water).
The ingredients are now all entered upon the prescription, but their respective quantities have not yet been decided on. We proceed, then, by first taking into consideration the total quantity of the medicament required, which, in this case, as the preparation is intended to purge the patient, need not embrace more than one or two doses. As it is well to provide for a repetition of the dose, in case the medicine should not act sufficiently, we will decide upon two doses in all. Now, the average adult dose of Castor-oil is about a tablespoonful, or half-an-ounce, and as we want two such doses we insert the sign and numeral f℥j, or simply ℥j, opposite the title of the oil, which is written in the genitive case. But to emulsify it properly we need about one-half as much of the emulsifying agent, and we may express this by writing for half-an-ounce of yolk-of-egg, or for the yolk of one egg, or for one yolk-of-egg, which weighs about half-an-ounce. This would be expressed in Latin by either of the following methods, viz.:—
Vitelli semi-unciam, (℥ss). One half-ounce of Yolk-of-egg.
Vitellum ovi unius, (j). The Yolk of one egg.
Vitellum unum, (j). One Yolk-of-egg.
As the word Vitellus means Yolk-of-egg, we may omit the word Ovi, and accepting the latter as the best style, insert the numeral j opposite the word Vitellum, which is properly in the accusative case. The whole quantity so far specified is one ounce and a half, and if we add two and a half ounces of diluent, we shall have a four-ounce mixture, or the full of a regular-sized bottle, as found in the shops. There being considerable viscidity already present in the emulsion we do not need much syrup, so we assign to the Syrup of Ginger the odd half-ounce, leaving two ounces of the Water to make up the total bulk of four fluid-ounces.
The prescription now only requires for its completion that the subscription and signature be added. We proceed to admonish the dispenser by telling him to mix the ingredients together, and therefore write the word "misce," or the abbreviation "M" commonly used therefor; and to further point out the nature of the preparation we add,—"let be made an emulsion," or in Latin, "fiat emulsum,"—the passive verb taking as predicate-nominative the thing into which the making is to be. The final words "Label"—or "Write thus"—are expressed by the term "Signa,"—followed by the directions for the patient or the person who is to administer the medicine, which should be in English, though they may also be written in Latin. Our completed prescription will stand thus,
|For Miss Graham.||June 10th, 1894.|
|Tere bene simul: dein adde—|
|M. fiat emulsum.|
|Sig.—"One-half at once, to be repeated next day if required."
The last entry of the inscription might also be written thus—"Aquae Cinnamomi, quantum sufficiat ad ℥iv," meaning "of Cinnamon-Water as much as may be necessary to [bring the whole quantity to] four ounces,"—usually expressed in contracted style, thus—
- Aq. Cinnamomi, q. s. ad ℥iv.
This style is preferred when any of the quantities are approximations, and the final item cannot be exactly stated to secure a certain total. In the foregoing case, the one yolk-of-egg might measure a little more than the half-ounce assigned to it; but by using the q. s. ad style at the end, we make sure of getting a total of exactly four fluid-ounces.
In more complicated prescriptions, the mode of reasoning is precisely the same; practice, care, and knowledge of the whole subject being necessary to the production of those elegant prescriptions which are correctly termed "magistral," as the work of a magister, or master of his business.
Metric Prescriptions are written or read with sufficient accuracy, by considering a gramme as equal to 15 Troy grains, and a cubic centimeter (or milliliter) as being equal to 15 minims or one-fourth of a fluid-drachm. All other terms, units or prefixes, belonging to the metric system, may be wholly ignored by both physician and pharmacist. The decimal point after the gramme or the cubic centimeter should always be replaced by a line, so as to avoid errors, which in many cases might prove serious, from the misplacement of a point, the dropping of an ink-spot, or the intrusion of a fly-speck.
The simplest method of writing a prescription in metric terms, is to first write it as though prescribing but one dose of each ingredient in grains or minims and decimals thereof; then by substituting the term "grammes" or "cubic centimeters" for the grains and minims the prescription is correct for fifteen doses in metric terms. For example,
|One Dose.||15 Doses Metric.|
|Rx.||Quininae Sulphatis,||gr. j||1 ||
|Strychninae Sulphatis,||gr. 1/64 or 0.016|||||016|
|Ext. Glycyrrhizae Fl.,||♏iv||4 ||
This gives a two-ounce mixture approximately, of which the dose would be "a teaspoonful thrice daily." The above rule will answer for all liquids except those which are very heavy (as Syrups and Chloroform), or very light (as Ether). Measures may be entirely discarded and all fluid quantities expressed in grammes. The average drop of water may be taken as equal to 0.05 c.c., the teaspoonful to 5 c.c., the tablespoonful to 20 c.c., the ℥ to 30 c. c. (or grammes), and ℥viij to 250 c.c.
Renewals.—It would be advisable for physicians to always write the words "Non Repetatur," or some similar direction, on all prescriptions which should not be repeated without their sanction. By so doing they would doubtless cut off a good many renewal charges from the receipts of druggists who would fear the legal consequences of disobeying the mandate. This inconvenience to the drug-seller would be more than compensated for in the protection to the drug-taker, who too frequently carries in his pocket-book a stock of recipes for his various complaints; and in protection to the physician, who by giving up the dispensing of his own medicines has placed it in the power of the druggist to connive at a direct robbery of the just reward of professional skill and knowledge.
Principles of Combination include certain maxims which should never be lost sight of. To prescribe as few remedies as possible, and to order no powerful drug without a distinct idea of its office in the prescription, are, perhaps, the chief; to which may be added another, namely—to give powerful agents by themselves when required for impression on the system.
Medicines are combined for several purposes,—(1), to increase, correct or modify the action of another medicine; (2), to obtain the joint action of two or more diverse remedies; (3), to obtain by chemical reaction a special combination, which is either a new remedy, or which acts as a new remedy; (4), to give a suitable form for administration, or for preservation.
A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.