PRESCRIPTION is the term applied to the written direction or receipt given by the physician or surgeon to the chemist for the preparation of it medicinal substance suitable to a special case. In prescribing, the medical practitioner may either order an officinal or all extemporaneous compound. Officinal compounds (or preparations, as they are fre quently termed) are those for which formulm are introduced into the national pharma copoeias, and are therefore supposed to be always at hand in the laboratory of the pensing chemist (such, for example, as mistura femi composita, pelvis ipecacuanhe compositus, confatio aromatica, etc.); while extemporaneous compounds are those which are devised on the instant with the view of meeting the various peculiarities which almost every case of disease presents. " Too much importance," as Dr. Paris very truly observes, " cannot be assigned to the art that thus enables the physician to adapt and graduate a powerful remedy to each particular case by a prompt and accurate prescrip tion. If he prescribes upon truly scientific principles, he will rarely, in the course of his practice, compose two formuke that shall in every respect be perfectly similar, for the plain reason, that he will never meet with two cases exactly alike."—Pharmacologia, 9th ed., 1843, p. 374.
The author whom we have just quoted, and who is the highest English authority on the subject, lays down five objects which the physician should have in view in the con struction of an extemporaneous formula or prescription. They are: 1. To promote the action of the principal medicine (or, as he terms it, the basis) of a formula. 2. To cor rect the operation of the basis. 3. To obtain the joint operation of two or more medi cines which act in totally different ways. 4. To obtain a new and active remedy not afforded by any single substance. 5. To select an eligible form.
The first object may be attained (a) by combining different preparations of the same substance, as, for example, tincture of seams with infusion of senna in the ordinary black draught; or (b) by combining different substances of a similar action, as, for example, opium with hyoscyamus or conium; or sulphate of magnesia with the preparations of senna; or quinine with the preparations of iron. The second object may be attained in various ways. For example, the addition of extract of hyoscyamus to the compound extract of colocynth renders the purgative action of the latter much less griping, but not less efficacious; the addition of dilute sulphuric acid to a solution of sulphate of mag nesia renders that purgative salt less liable to gripe, and makes it sit easier on the stomach; and extract of eleterium, if given in hot brandy and water, acts equally pow erfully as a hydragogue cathartic without causing the depression of the vital powers, which it often oceasious if given alone. As an illustration of a mode of attaining the third object, we may refer to the operation of purgatives and of diuretics. If we administer a purgative which acts mainly in increasing the peristaltic motion of the intestines, their contents will be urged forward and evacuated, but the operation will be s]ow and diffi cult, and probably be accompanied with griping; but if we combine this medicine with one which acts by increasing the flow of fluids into the intestine, the purgative action will be increased and quickened, and all griping will. be avoided. A combination of
foxglove, squill, and blue pill or calomel will act much more powerfully as a diuretic than any one of the substances taken alone; and they probably all act in different ways on the system. The fourth object is usually attained by chemical decomposition. The activity of the Mistura Ferri Composita is due to the carbonate of iron which it contains, and which is yielded by the double decomposition of the two ingredients of the mixture, sulphate of iron and carbonate of potash. By prescribing a mixture of solution of iodide of potassium and corrosive sublimate, we obtain an extemporaneous formation of biniodide of mercury. The h :.ck wash (see LINL%IENTS) owes its active ingredient to the decomposition of calomel by lime-water. In some cases, where no chemical action is apparent or probable, a mixture of two or more drugs seems to modify the physiolog ical effect of each ingredient. For example, Dover's powder contains as its active ingre dients ipecacuanha and opium, and yet in well-regulated doses it neither exhibits the nauseating properties, of the former nor the narcotic influence of the latter substance. The fifth object, the selection of the most eligible form of the remedy, is of extreme im portance. The physician here has to determine whether he shall prescribe his remedy in the form of pill, pOwder, or mixture; whether he shall administer it as an injection into the lower bowel; whether the patient shall (in certain cases) inhale it; etc. As a general rule, we should accommodate the form and flavor of our remedies, provided we do not sacrifice their virtues to the taste of the patient, who usually prefers pills to draughts or powders. The unpleasant taste of many medicines which must be given in the fluid form may often be obviated by the skill of the prescriber. Castor oil, cod-liver oil, and copaiba are most easily taken on the surface of orange wine, or water containing a bitter tincture, care being taken to moisten with water the edge or rim of the glass at the part applied to the mouth. The taste of solution of potash and of lime-water is best covered with milk; and the disagreeable flavor of senna is said to be concealed if its infusion is made with strong tea, In conclusion it may be remarked that in this country it is the custom to write pre scriptions in the Latin language, to abbreviate well-known words, to use symbols for weights and measures, and to commence each prescription with the symbol 13, which mignifies Recipe, take. As an illustration, we append a prescription for a touic draught: (Name of Patient.) ]; Tutus. Calumbre, f. 3 ix Tinct. Calumbre, f. 3 Acid. Sulph. Dilut., nix Syrup. Aurant., f. 3 iss M. Fiat Ilaustus ter goutidie sumendus.
Date (in Latin). (Initials or name of prescriber.)