This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
1. There are medicines which appear to have the property of directly stimulating the true bronchial secretion, by contact with the secreting structure, to which they are brought with the blood, having entered the circulation by absorption from the stomach, or other surface of application. Such are squill, seneka, ammoniac, etc. it is not impossible that they may act through sympathy between the gastric and bronchial mucous membranes; but we have no proof that this is the fact; and analogy would lead to the conclusion, that they operate solely by direct contact, at least in their capacity of stimulants to the secretory function. The matter expectorated under their influence is usually a somewhat opaque mucus, showing that they increase the exfoliation of the cells, along with the production of the proper mucus, and thus merely augment the normal action of the membrane. Some, if not all of them, have the property of exciting also other secretory functions; but, with a few exceptions, their characteristic tendency is to the air-passages.
2. The blood-vessels of the bronchial mucous membrane, and of the pulmonary air-cells, are often irritated and actively congested beyond the secreting point. Hence the dryness of the membrane, and the want of expectoration, in the early stage of bronchitis. if the excitation be somewhat reduced, without being entirely suppressed, it may be brought to the point at which the proper function is merely stimulated by the increased supply of blood, and the secretion will now be restored, and in a degree beyond the normal amount. But it is not only the proper secretion that is increased. The same thing happens necessarily to the simpie elimination or exhalation through the coats of the vessels, and the watery discharge is consequently augmented along with the proper mucus. in this way, nauseating substances, and the arterial sedatives, operate not unfrequently as expectorants. Under the influence of nausea, the vessels of the lungs, like those of the skin, become relaxed; and, under that of the arterial sedatives, the force of the circulation is directly reduced. ipecacuanha and lobelia act in the former method, tartar emetic probably in both. But, as these medicines enter the circulation, it is probable that they also have a direct influence on the secretory function, though not greater than that which they exercise on other functions, especially that of the skin.
3. Anything which moderately excites the circulation in the lungs and air-passages may prove expectorant. Both the secretory function is stimulated by the more copious supply of blood, and the pulmonary exhalation is increased by the fulness of the vessels. Some persons always expectorate after a meal, which gently excites the general circulation. Laughter often produces the same effect, to a very considerable extent, by stimulating especially the circulation of the lungs. I have often known copious expectoration to come on after hearty fits of laughter; which, therefore, may serve as a useful remedy in chronic bronchitis. Sometimes the exercise of the chest in speaking has a similar influence. The operation of the special stimulants of the bronchial secretion is no doubt augmented by the property, which some of them have, of moderately stimulating the circulation also. They not only excite the cells themselves, but furnish more abundantly the material upon which they operate.
4. There is another altogether distinct method in which expectoration is promoted. The medicines which operate in this way do not increase the amount of matter thrown out into the air-passages; but, on the contrary, sometimes diminish it. Not unfrequently, in the advanced stages of pulmonary disease involving the bronchial tubes, and in the chronic condition of the same affections, there is a superabundant production of bronchial fluid, more than can be conveniently discharged, and sometimes very much embarrassing respiration, and endangering life. This is generally, under the circumstances mentioned, the result rather of a relaxed and debilitated state of the tissue than of its undue excitation. it may be compared to the colliquative sweats, diuresis, and diarrhoea of debility. To correct this condition, and enable the lungs freely to expectorate the contents of the tubes and air-cells, the quantity of liquid must be reduced. This effect is produced by the stimulant expectorants. it has been suggested that they might act by causing the absorption of a portion of the exuded liquid, and thus bringing it within the capacity of the lungs to manage. But it is scarcely probable that a copiously eliminating tissue tan be made also to absorb actively. Nor have we any proof that mucus is capable of being reabsorbed. The probability is, that the expectorants act simply by stimulating the bronchial membrane, perhaps sometimes altering its condition, thereby diminishing the amount of elimination. The vessels and secretory cells, having more vital cohesion or tonicity, under the influence of the medicine, become more retentive; and, the amount of extravasation being diminished, the lungs gradually throw off that already accumulated. The expectorants here have/this advantage over simple general stimulants, not only that their influence is more directly exerted upon the secreting tissue, but that, being special excitants of the function, they do not abolish it, and thereby endanger congestion of the lungs; but, after having reduced it within due limits, sustain it in a state of moderate augmentation, calculated to relieve the diseased condition of the membranes. Squill, seneka, ammoniac, assafetida, and the balsams often act usefully in this way.
5. it is, moreover, highly probable that the stimulating expectorants not only operate by diminishing the excess of secretion in debilitated cases, but also facilitate or invigorate the act of expectoration by exciting the contraction of the muscular fibres of the bronchia, and by promoting the ciliary movement, which nature has provided as a means of passing the bronchial fluids on to their place of exit.
6. Another method in which relief is often afforded in pectoral diseases, associated with great debility, is by stimulating the respiratory muscles. in paralytic and otherwise low states of the system, it not unfrequently happens that the patient has insufficient muscular power to throw off from the lungs the secreted matters with which they may be loaded; and death is inevitable unless relief can be obtained. This condition exists in the advanced state of severe bronchitis and pneumonia, particularly in infants, and is very common in phthisis. The medicines which now operate as expectorants are those which stimulate the nervous centres, so as to give greater energy to the muscles of respiration. Wine-whey or other preparation of alcohol is here useful; but the most efficient remedies are those, which, with a stimulant power, have, in some degree, a special tendency to the lungs. Such are carbonate of ammonia, assafetida, garlic, and the oil of turpentine. These not only increase the muscular power, but tend also to control the bronchial or pulmonary affection, in which the difficulty originates.
7. Local applications, made to the broncial mucous membrane, sometimes favour expectoration; and, according to the state of the affection, and the nature of the substance used, may be made to answer most of the above indications. They are effected by inhalation. in somewhat excited and dry conditions of the bronchial membrane, the inhalation of watery vapour, at a rather low temperature, so as not to be excitant through the heat, may, by relaxing the vessels, sometimes favour secretion. in a somewhat atonic condition, on the contrary, the same effect often follows the inhalation of stimulant substances, in moderate degree, as chlorine very much diluted, the vapours of iodine, those of tar, and the fumes from burning resin. These are also useful in that condition in which the secretion is too abundant, in consequence of excessive relaxation or weakness of the tissue.
In an acutely irritated or inflamed state of the air-passages, from the larynx downward, the nauseating or relaxing expectorants, such as ipecacuanha and tartar emetic, are indicated, and are among the remedies most constantly resorted to. This condition is presented in the earlier stages of common catarrh, special laryngo-tracheitis and bronchitis, measles, hooping-cough, and the different pectoral inflammations attended with bronchia] irritation.
In a somewhat more advanced stage, when the activity of the inflammatory excitement has abated, but expectoration is defective, the direct expectorants, which are too excitant for the earlier period of the disease, may be resorted to with much advantage, to aid in unloading the still congested vessels. in this condition, squill and seneka may often be advantageously used. They are too stimulating, in their local action, for the state of highest excitement. Should any doubt be entertained as to the sufficient subsidence of the inflammation, they should be combined with the medicines of the first class, which, by their relaxing influence, may obviate an over-stimulation of the vessels.
In a still more advanced stage of the same affections, when the membrane is enfeebled, either with or without a free expectoration, and in chronic laryngeal or bronchial diseases of the same kind, the stimulant expectorants are decidedly indicated, in order to give vigour to the membrane, and enable it to resume its healthy condition. it is not im-possible that some of the expectorants, adapted to this stage, exert also an alterative influence over the membrane, favourable to its restoration to health. The aim of the practitioner should always be to graduate the degree of excitation to the apparent state of debility, and to select the more or less stimulant expectorants accordingly. Among the least so are squill and seneka, among those of greater stimulant power, though probably less efficient as mere expectorants, are ammoniac, assafetida, garlic, carbonate of ammonia, etc. Advantage will often accrue from combining the two sets together, whereby the more expectorant properties of the one, and the more stimulating of the other, may be obtained in conjunction. Bronchitis and pneumonia, in their very advanced stages, particularly after suppuration has commenced; the same affections less advanced, occurring in much enfeebled constitutions, or as-vol. II. - 43 sociated with typhoid disease; and chronic catarrhal affections attended with excessive mucous or muco-purulent secretion, as bronchorrhoea, catarrhus senilis, and humoral asthma, are complaints which offer indications of the kind alluded to.
In all cases in which the lungs are likely to be overwhelmed by secretion or liquid accumulation in the bronchia and air-cells, or in pulmonary cavities, which the patient has not the muscular power to discharge, there is an indication for the most stimulant of the expectorants, and those calculated to operate with special force on the nervous centres, as carbonate of ammonia, assafetida, and garlic.
Still another indication which the expectorants fulfil is, by the production of copious secretion into the air-cells and bronchial passages, to act both depletorily and revulsively upon the inflammation of the proper tissue of the lungs, and even that of the pleura. Hence their utility in pneumonia and pleurisy, independently of the good effects they produce, in those complaints, in the relief of the accompanying bronchial irritation.