This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Pharmacy includes both the general preparation of drugs from crude natural products and their combinations with other substances, so as to render them either more effectual or more easily administered.
The great rule for the administration of medicines is (1) curare (2) cito, (3) tute, et (4) jucunde - that they shall not only (1) cure, but that they shall do so (2) quickly, (3) safely, and (4) pleasantly. According to this rule many prescriptions contain four ingredients, viz.: (1) the substance which is to cure, or the basis; (2) the adjuvant to help it; (3) the corrective to prevent any bad effects; and (4) the vehicle to make it pleasant to take. This rule, however, is carried out not only in written prescriptions, but in those also which have been adopted by the profession at large, as a means of saving labour and time in the routine of practice, and embodied in the Pharmacopoeia as useful preparations.
Formerly we were dependent for our medicines chiefly on the crude products of the animal, vegetable, and mineral kingdoms. As chemistry advanced various inorganic compounds were discovered and added to the Materia Medica, and as our knowledge of this science becomes greater and our power of preparing various organic bodies increases, we find that such bodies are becoming more and more introduced into medicine. As examples of these, we may take carbolic acid, chloral, chloroform, ether, hydrocyanic acid, iodoform, nitrite of amyl, salicylic acid, and kairin.
We seem now on the verge of discovering the mode of preparation of many organic alkaloids, and when this has been done, the vegetable Materia Medica will be less important than it is now, inasmuch as it is probable that, by using artificial alkaloids, prepared always under similar conditions, we may obtain purer products and greater constancy of action than we can at present from the natural active principles.
Recent discoveries have shown that plants generally contain active principles so closely associated, that the mixture was regarded as a pure alkaloid, and yet these drugs have very different and sometimes opposite physiological actions. Thus ordinary coniine usually contains pure coniine and methyl-coniine, the former of which paralyses the motor nerves, while the latter paralyses the spinal cord. Extract of physostigma, and supposed pure physostigmine, or eserine, have been found to contain two active principles, viz. physostigmine having a paralysing action, and calabarine having a tetanising action on the spinal cord.
The power which chemistry now gives us also of modifying the chemical constitution of organic bodies and therewith their physiological action, will almost certainly enable us to treat disease much more perfectly than we can at present. For such modified drugs, however, we must be indebted to the chemist. He will prefer to operate on substances which have been already prepared by himself rather than on crude drugs obtained from plants. But at present we are still dependent on the vegetable kingdom for a large number of our most useful remedies. In plants they are associated, as a rule, with quantities of woody tissue which is quite inert and indigestible, and which would interfere very much both with their easy administration and with their action.
Sometimes the crude drug is given in the form of a simple powder, without any admixture, as in the case of guaiac given in tonsillitis, where it is advisable to have the local action of the drug on the throat, as well as its general action on the system. Sometimes the powder may be readily given by enveloping it in a wafer, and swallowing it with a little water, and at other times it is made up with saccharine, and more or less adhesive substances, into the form of a confection or bolus; or suspended in water by means of mucilage in the form of a mixture. Usually however the active parts of the drug are extracted by means of solvents, and either given in solution, or in the solid form, after the solvents have been evaporated. There are a number of preparations according to the solvents used, and the mode in which they are applied. Probably the most convenient arrangement is not to take the groups of preparations according to the solvents or mode of preparation, but alphabetically for the sake of reference.
Groups of Officinal Preparations.
The letters B.P. stand for the British Pharmacopoeia of 1885, and U.S.P. for the United States Pharmacopoeia of 1883. When the letters B.P. or U.S.P. precede the name of a class or of a substance, they indicate that it is contained in the corresponding pharmacopoeia only, and not in the other. They succeed the name or are omitted when the class or substance occurs in both pharmacopoeias. When there are differences between things bearing the same name in the British and United States Pharmacopoeias, the letters B.P. are placed after the descriptions of that contained in the British, and U.S.P. after that of the United States Pharmacopoeia.