Diuretics. Under this class of medicinal agents it may be observed that, whenever a medicine is liable to produce effects different from those we desire, its combination with similar remedies is particularly eligible, by which the action of the basis may be directed and fixed; thus the individuals which compose the class of Diuretics are uncertain in their operation, and disposed when exhibited singly to produce diaphoretic, and other contrary effects; it is, therefore, in such cases, highly judicious to unite several of them in one Formula, by which we increase their powers, and are more likely to ensure their operation. Formulæ 101, 103, 108, 109, 110, 111, 115, are constructed upon this principle.
Diaphoretics. Our maxim, “Vis Unita Fortior,” certainly applies with equal truth to this class of medicinal agents. Form. 122, 124.
Expectorants. More is frequently to be gained by the co-operation of these remedies than can be obtained by the exhibition of them separately, as in Form. 134, 135.
Demulcents do not appear to obtain any other benefit from combination than, occasionally, a convenience and efficacy of application arising from a suitable degree of consistence and solubility. See article “Trochisci.”
The operation of the law which has thus formed the first object of this inquiry, will be found, like every other, to have a natural and well defined limit; it is easy to perceive that by multiplying the number of ingredients too far, we shall either so increase the quantity and bulk of the medicine as to render it nauseous and cumbersome, or so reduce the dose of each constituent as to fritter away the force and energy of the combination.
The propriety of combining several stimulants, of the diffusible class, in one formula, has been questioned on different grounds. Dr. Chapman, in his work on Therapeutics, adduces some arguments on this point, which, although they fail in establishing his general position, certainly suggest an important exception to the practice in question; “by directing,” says he, “stimulating remedies, separately, we shall economise our resources in many lingering diseases.” The justness of this statement must be admitted to its fullest extent, and practitioners will, on certain occasions, do well to act in conformity with the views that suggested it; for instance, in the feeble forms of protracted fevers, where the indications are to be met with the continued action of stimulants, it will certainly be salutary to alternate the use of camphor, ammonia, and other remedies of a similar nature, in preference to presenting them all at once in combination, so that the system may not lose its susceptibility by the continued impression of the same stimulant; the same motive should induce us, on particular occasions, to employ in succession different narcotics, for each of them affects sensibility in its own peculiar manner.[[244]] The nervous system, as Richerand has very justly observed, may be compared to a soil, rich in different juices, and which requires the cultivator to plant the germs of a diversified vegetation to develope the whole of its fecundity; to insure a perpetual return, therefore, it will be right to sow a succession of different seeds. Hoffman also has offered us some advice upon this subject; he directs us in the treatment of chronic diseases to suspend the administration of remedies, at intervals, and afterwards to resume them, lest the system should become habituated, and ultimately insensible to their influence.
But there remains for our investigation a still more important precaution respecting this law of medicinal combination;—that, in combining substances in the manner, and for the object just related, the practitioner should be well satisfied that their medicinal virtues are in reality practically Similar, or he will fall into an error of the most fatal tendency; it has been already shewn, and I hope I shall not be considered tedious by again directing the reader’s attention to the fact, that medicines are not necessarily similar because they have been arranged in the same artificial division of remedies; in order to establish a perfect similarity their operations must be found by experience to continue similar under every condition of the human body; and that, moreover, they must owe such similarity to modes of operation which are compatible with each other, and consonant with the general mode of cure; we have only to refer to the history of Diuretics (page 92) for a full illustration of this important truth; thus Squill, Calomel, and Digitalis, are each powerful Diuretics, but nevertheless they cannot be considered similar remedies, since Digitalis will entirely fail in its effects in the very cases that Calomel and Squill succeed; and Squill will prove inert when Digitalis is capable of producing the most powerful influence; this arises from their modes of operation being dissimilar, and consequently requiring for their success such different states of the living system. Squill, it will be seen, acts primarily on the urinary organs, by stimulating the secreting vessels of the kidneys; Mercury, on the contrary, acts primarily on the absorbents, and secondarily on the kidneys; whereas Digitalis produces its effects by diminishing arterial action, and increasing that of absorption.
Dr. Blackall, in his “Observations upon the Cure of Dropsies,” has offered some remarks so valuable in themselves, and so illustrative of this important subject, that I shall take leave to quote the passage. “Many physicians,” he observes, “are fond of combining Squill, Calomel, and Digitalis, as a diuretic in dropsy; a practice unsafe, and not very decidedly possessing the merit even of being consistent. Digitalis greatly depresses the action of the heart and arteries, and controls the circulation, and it seems most unreasonable to believe that its curative powers can be independent of such an effect; on the other hand, Mercury, if it does not pass off quickly, is always exciting fever, and raising and hardening the pulse; speaking from experience, where the urine is coaguable, and Digitalis agrees, both the others are, often at least, positively injurious. On the contrary, where the urine is foul, and not coaguable, and Squills with Calomel render service, I have on that very account, made less trial of Digitalis, and cannot therefore speak of it from much experience.” See Form. 103, and the note thereon.
The individual medicines which compose the class of Diaphoretics vary no less in their primary operations, as the synoptical arrangement at page 99 very fully exemplifies; thus, in the cure of intermittent fevers, diaphoretics are useful both in the paroxysm, and during the intermission; in the first case they shorten its duration; in the second they support the tone of the extreme vessels, and prevent its recurrence; but in these opposite states of disease a very different kind of diaphoretic is required—to fulfil the first indication, a cooling and relaxing one is necessary; to answer the second, the stimulating diaphoretic is exacted; the one may be said to solicit, the other to extort, perspiration. So again Emmenagogues can only be considered relative agents, since the suppression of the catamenia may depend upon, or be connected with, very different states of the system; in some cases with a diminished, and in others with an increased state of excitement; for on many occasions the suppression of the menses is the effect, and not the cause of disease; Boerhaave has very justly observed, that it is a most dangerous error to ascribe all the diseases of young females to a retention of the catamenia, which often do not appear because the patients are disordered from other causes. If, therefore, we were to attempt a combination of the several medicines which have gained reputation as Emmenagogues, it is very obvious, that we should bring together an assemblage of adverse and incompatible remedies; nor would the physician be less inconsistent were he to combine Expectorants, without a due regard to their modes of operation; it is only necessary to observe their classification, as presented at page 102, to become satisfied how greatly the success of such remedies must depend upon their scientific adaptation to each particular case.
The class of Antispasmodics may likewise embrace remedies of the most opposite tendency, for spasm may occur under the most opposite circumstances—in an extreme condition of weakness, as in nervous affections, and in an highly excited state, as in cholic, &c.; it is hardly necessary, therefore, to point out the mischief that must arise from the fortuitous and indiscriminate admixture of the individual substances which are thus unavoidably arranged in the same artificial classification. Bark and Steel are also too often considered as equivalent Tonics; in Dropsy, says Dr. Blackall, it is far otherwise, the former being infinitely to be preferred after the dropsy of young persons, of acute disease, and of sound stamina; the latter being suited to a vitiated rather than to a feeble habit, and indicated more by a pale sallow complexion, and a want of red colour in the blood, as shewn by the paleness of the lips, than by any other signs. Need we then adduce farther illustrations of the obvious but important fact, that the terms employed to denote the different classes of remedies are frequently but relative ones, expressive of effects which are produced only in reference to a particular state of the living body? and as this necessarily varies in different states of health and disease, it follows that medicines are convertible agents, and that when we attempt to institute general rules respecting their administration, without taking into consideration the constitution and circumstances of the patient upon whom they are to operate, we shall generally be disappointed in the result. We may say of medicines what Van Swieten said of diet, “to assert that such, or such a thing be wholesome, without a knowledge of the condition of the person for whom it is intended, is like a sailor pronouncing the wind to be fair without knowing to what port the vessel is bound.” Boerhaave was so fully impressed with this truth that he exclaimed, “nullum ego cognosco remedium, nisi quod tempestivo usu fiat tale.”