This section is from the book "The London Medical Dictionary", by Bartholomew Parr. Also available from Amazon: London Medical Dictionary.
Of Medicines. In the rage of reformation, it is not uncommon to step beyond the proper limits; and, in almost every science, it is necessary, in different eras, to review dispassionately the conduct of its professors; to correct, at times, their intemperate zeal, or to supply their omissions. Physicians have for many years aimed at simplicity in prescription, with propriety and success; but they have sometimes failed, in wholly rejecting combinations with which their ancestors succeeded. And it was rather a spirit of empiricism than philosophical induction which gave a general currency to Dover's sweating powder, and many of Ward's compositions.
To check, in some degree, the rage of simplicity, and the general tendency to too great refinement, we shall, from the different classes in medicines, select some instances, where combination is not only defensible but advantageous. We have already hinted at this subject under the head of cathartics, and pointed out the paper of Dr. Fordyce on the same subject. Though we may employ some of his instances, we shall not servilely follow his steps; but in the principal part of this article follow a different direction.
In the exhibition of emetics, we are often disappointed, by the medicine remaining inactive in the stomach, and escaping, with its stimulant powers unimpaired, into the intestines. The addition of an antimonial to the ipecacuanha may quicken its action; but this is subject to a similar inconvenience. By the addition of a few grains of the white vitriol, we can often, with either of the others, produce the effect. A sedative emetic, less dangerous than the tobacco or the foxglove, would be a great acquisition to the materia medica; but, even at present, in some pulmonic cases, the foxglove may be actively given for this purpose. The union of the squills with the ipecacuanha has often been highly useful, and equally so with the antimonials.
In the class of cathartics, combination is often essentially necessary. We have distinguished cathartics as operating by increasing the secretions from the glands of the chylopoietic viscera, and thus affording the natural stimulus to the intestines; as increasing the action of their moving fibres, by a stimulus peculiarly their own; or, as occasioning an extraordinary effort of the constitution, to throw off a poisonous substance introduced. It will be obvious, by uniting the two first, we gain many advantages. The effect of rhubarb, for instance, will be quickened and increased, if the polycrest salt assists in increasing, at a more early period, the motions of the alimentary canal; soap will sheath the acrid particles of aloes, and extract of jalap, while it assists their action; and the warmer gums, as in Dr. Fordyce's formula, gently stimulate the superior part of the canal, while they sheath and mitigate the too great acrimony of some of the ingredients. The old formulas of manna with the salts, quickened by some of the more active tinctures, or occasionally with metallic preparations, though apparently a disagreeable and discordant union, had many advantages, which are, in vain, expected from the more elegant formulae of modern times. In general, the more gentle laxatives should be quickened by the more powerful purgatives; and the latter (if indicated), softened by the oily, saccharine, the mucilaginous, or the saponaceous cathartics. There is, perhaps, no class of medicines in which greater latitude of combination may be allowed with advantage.
The subject of diaphoretics we must not anticipate; yet in this a judicious combination produces the most singularly beneficial effects. Generally speaking, the fluids are thrown to the surface by the stimulus of warmth, or other powers exciting the action of the heart and arteries. This stimulus, however, requires regulation; for we have found (see Cold), that excess of temperature is unfavourable to the discharge from the skin. Stimulus, when fever is not present, will, however, often succeed; but, in general, it requires the addition of a relaxant. Thus opium has, in every age, been the chief ingredient in sudorifics. But Dover refined on the former plans, by adding another relaxant; Ward, by the union of the white hellebore, which he, perhaps, supposed to be a stimulant, but which acted probably in a different way. Some poisonous medicines, by exciting nausea, relax the skin, and prove diaphoretic. Of this kind is the veratrum album, which Ward employed; and all the variety of narcotic vegetables will produce the same effect. In combination with the warmer stimulants, therefore, a great variety would probably form useful diaphoretics, did we want any more powerful than those we possess.
Diuretics are of a similar nature; and, independent of the more immediate and active stimulus conveyed to the kidneys, narcotics, by inducing general relaxation, promote greatly the flow of urine Some combinations of the two kinds we have employed with effect; and, if
Bacher's tonic pill is useful, it is from a combination of this kind. The necessity of the union is sufficiently perceived, by joining aromatics with the foxglove. Why not rather the oils of juniper or turpentine?
Errhines are also of two kinds, the stimulant and evacuant: these are usually combined. We have but one internal sialogogue: but the Hindoo unites the stimulant with the sedative in the preparation of his betel.
In the exhibition of emmenagogues we occasionally combine with advantage, the more general stimulants and tonics with the topical stimulants of aloetic purgatives; sometimes the latter with relaxants: and, under lithontriptics, we have mentioned the union of the bitters, designed to counteract the calculous diathesis, with medicines that act on the calculus itself. We have even expressed our doubts, whether refinement has not too far simplified the medicine of Mrs. Joanna Stephens.
Medicines of a more general action do not so frequently require combination. We allude to stimulants and sedatives. Astringents and tonics, however, demand a more exact attention, properly to appropriate the medicine to the disease, as each is seldom without an admixture of the other, and a stimulant principle is sometimes combined. But this part of the subject requires a minuteness of detail, which can only be advantageously pursued when connected with the consideration of separate diseases.
In many of these classes, Dr. Fordyce seems to think, that the union of two or more substances of the same class can be more easily borne, and be more effectual, than the same bulk of a single medicine; as water, when saturated with one salt, will dissolve a portion of a different kind. It is not improbable; and while, as in the classes just alluded to, we are measuring the degree in which we shall add the wanner to the purer astringent, we may perhaps increase the activity of the medicine. On this subject we cannot properly decide; for we, too, are of "St. Thomas, and hard of belief."
Another method in which combination will be useful is, where two indications can be at once answered by the union of different medicines. The instance given by Dr. Fordyce is the union of tormentil with ipecacuanha in old diarrhoeas. The one strengthens the bowels, while the other determines to the skin: an effect highly advantageous in the cure. This consequence of combination is peculiarly important, and we would strongly recommend it to the practitioner's attention: but it will be obvious, that it rather relates to the management of particular diseases; and to pursue the subject would require a volume. See Transactions for improving Medical and Chirurgical Knowledge, vol. ii. p. 314.
 
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