Sometimes the unpleasant or perverse operation of a medicine may be obviated by changing the form of its exhibition, the period at which it is taken, or the extent of its dose; Dr. Cullen, for instance, found that the nauseating operation of Camboge might be obviated, by repeating small doses at short intervals. (89.)
Before quitting the present subject, it deserves notice, that there is frequently a chemical condition of the stomach that may interfere with the mild operation of a medicine, and may therefore require consideration: this is particularly exemplified in the action of those antimonial preparations which are liable to become emetic and drastic by the presence of an acid; it is, for this reason, very eligible to guard such substances with antacid adjuncts. See Antimonii Sulphuretum, and Form. 125, 128. There is also, upon some occasions, an irritable state of the primæ viæ depending upon a deficient secretion of mucus, which renders even small doses of any active medicine mischievous; mucilaginous decoctions in such a case will offer the readiest corrigent; see Scammonia.
The vinous infusion of Colchicum appears to act more violently when acid is present in the stomach; small doses of Magnesia may therefore precede, and accompany its exhibition, with advantage.
III.
TO OBTAIN THE JOINT OPERATION OF TWO OR MORE MEDICINES.
A. By uniting those substances which are calculated to produce the SAME ULTIMATE RESULTS, although by totally different modes of operation.
It has been already stated, (page 152), that we may frequently combine substances together whose modes of operation are dissimilar, with considerable advantage, provided they be not physiologically incompatible with each other. We may illustrate this subject by a reference to the operation of purgatives; a series of medicinal substances may be produced, each of which has the property of exciting catharsis, but by a very different mode of action; one for instance stimulates the muscular fibres of the intestines; a second acts upon the exhalant vessels, and mucous glands; and a third exerts its influence upon the neighbouring organs, so as to produce an increased flow of their secretions into the bowels; but since such modes of action are quite compatible with each other, they may be simultaneously established, not only without any loss of efficacy, but with the most decided advantage; suppose, for instance, we administer a substance which, either from its insolubility or peculiar nature, acts exclusively upon the muscular fibres of the alimentary canal, its peristaltic motions will be undoubtedly thus increased, and the contents of the bowels evacuated, but the operation will be slow, and probably accompanied with considerable tormina; now it is evident that if to such a remedy we add those which can produce an increased flow of serous fluids, the effect will be both quicker and easier. The infusion of Senna is thus quickened and corrected by Soluble Tartar. In the same manner various substances included in the class of diuretics, which, although different, still if they be not adverse in their operation, may be conjoined; Digitalis and Potass are not similar, nor are they incompatible, for while the alkali, through the medium of the circulation, stimulates the secreting organs of the kidneys, the foxglove may, by its sympathetic action, rouse the energy of the absorbents. In the administration of diaphoretics we shall frequently derive additional force, as well as certainty, by combining those which act by relaxing the cutaneous emunctories, with those which prove diaphoretic by imparting a general increase of momentum to the blood.
B. By combining Medicines which have entirely different powers, and which are required to obviate different symptoms, or to answer different indications.
Arrangements constructed upon this principle constitute some of the most valuable remedies with which we are acquainted; they are in general extemporaneous, because their value depends upon their being varied and modified according to the symptoms and circumstances of each particular case. The following general elucidation of the subject may serve to demonstrate the nature and importance of such combinations.
Purgatives with Antispasmodics. The practice suggested by Drs. Stoll and Warren, in the treatment of Cholica Pictonum, affords a striking example of the expediency of combinations of this nature. It is found in that disease, as well as in others attended with spasmodic constriction of the intestinal canal, that purgatives produce no effects unless the spasm be allayed by combining them with Opium, (see Form. 71, 75, 76,) it is from such a cause that the purgative so popular with tailors and shoemakers, and which consists of Aloes with Sagapenum or Galbanum, affords such prompt relief in the spasmodic cholic to which they are subject.
Purgatives with Tonics. In the exhibition of cathartics how frequently it occurs in practice that the patient’s strength will hardly allow the evacuation; in such a case the addition of steel as a roborant (Form. 72, 92, 93,) or even of æther, or ammonia, as a diffusible stimulant, is strongly indicated: the Cheltenham waters offer a natural combination of this character. So again in the cure of dropsy we have often two indications to fulfil—to evacuate the water, and to support the strength of the patient; hence the necessity of combining brisk and stimulating purges, such as Scammony, Jalap, &c. with active tonics, (83.) In the treatment of amenorrhæa the same medicinal arrangement is not unfrequently indicated.