Sedatives may be defined to be those therapeutic agents which calm or diminish irritation, and rectify sympathetic innervation. They may be divided into general and special, the first exerting their medicinal influence upon the entire system, and the second producing their effect upon a special part.
Sedatives are commonly classed with narcotics, but as the latter agents act first as excitants before producing their sedative influence, and as they exert a special influence over the intellectual functions, are anodynes, and produce sleep, there is a marked boundary between the two classes. Again, sedatives are not ordinarily used to lessen pain or procure sleep, but as contra-stimulants or direct depressors of exalted activity either in the entire system, or in but a portion of it. From these facts we think a division of the two classes of agents may with propriety be made, notwithstanding the line of demarkation is not always very conspicuous between them.
Sedatives may either act directly upon the nervous system, producing sedation (direct sedatives), or their sedative influence may be dependent upon some other effect produced by them; sedation being dependent upon an exhaustion caused by the action of the agent, in this case we would name them indirect sedatives. Refrigerants exert an indirect sedative influence, as also do cathartice, emetics, diaphoretics, etc.; they depress the vital forces from their primary action, but their modus operandi differs widely from the direct sedatives.
Action of Sedatives.—Direct sedatives, like narcotics, are soluble in the fluids of the body, and are hence absorbed and conveyed by the blood to the part of the nervous system upon which they tend to act. That they are absorbed is proved by the fact, that their action is the same whether applied endermically, injected into the serous cavities, or under the skin. They are nerve medicines, producing their effect upon the nervous system entirely, and are thus like narcotics, transitory in their action. Some of them influence the entire nervous system, while others, unlike narcotics, expend their entire force upon some particular nerves.
In poisonous doses they may either derange or destroy nervous force, and interfere with the activities of the entire body or of a part. In the olden time the doses were often so large as to be depressant and poisonous, and if excitation and a frequent pulse were due to debility, they might extinguish the feeble flame of life. In medicinal doses, their influence is towards normal action, by giving right innervation. As a rule, frequency of pulse depends upon an excited innervation, and is associated with increased temperature. It is in these cases that physicians think of administering the special sedatives. But there are cases in which sympathetic innervation is enfeebled, and the temperature too low, but the pulse is rapid, as in cholera, yet a sedative like Aconite or Veratrum will prove a powerful remedy, by giving better innervation and circulation. The old idea that sedatives must be depressant, must be got rid of, as the dose we now use improves the powers of life.
Frequency of pulse is one of the most common symptoms of disease, and we are in the habit of saying—As is the the frequency of pulse, so is the gravity of the disease and the danger to life. Every function of life is influenced by the frequency of pulse, and is impaired as we note an increased number of pulse-beats per minute. As the pulse returns to a normal standard, all-the functions of life improve, and with the full establishment of a right circulation, convalescence commences.
In the hot stage of acute diseases, we notice a remarkable uniformity between the frequency of pulse, and the increasing temperuture. As the pulse becomes more frequent, the temperature goes up; as the pulse is brought down, the temperature comes down. The ratio is about ten beats of the pulse to one degree of heat. With a temperature maintained steadily above 103°, death progresses rapidly. With a pulse maintained steadily above 120 beats per minute, the patient is upon dangerous ground.
Whether we think of digestion, blood making and nutrition; or of excretion by way of the skin, kidneys, and bowels; or of a restful condition and good innervation from the brain and spinal cord; or of the development and activity of zymotic poisous, or the rapid propagation of disease-germs, we must take into consideration the condition of pulse and temperature. With a slower pulse and lower temperature the vital processes are re-established. With increased frequency of pulse and temperature, the vital processes are impaired, and the intensity of their poisonous materials increased.
In proof that their effects are transitory, we may mention the fact that in poisoning by hydrocyanic acid, when the quantity taken is not too large, if artificial respiration is maintained, and the arterialization and circulation is thus carried on for a time, the nervous system may recover from the deadly effects of the agent, and resume its normal function.
Sedatives reduce the momentum of the circulation by rectifying the innervation of the heart; the pulse becomes slower and better when the patient retains the recumbent position; but its rapidity may be increased by any muscular exertion, the increased action compensating for its diminished energy. They lessen the action of the respiratory organs; by lessening the sensibility of the pneumogastric nerve; they diminish the sensation of want of air, and hence, even if the motor nerves were not affected, respiration would be slower. As the respiration is slower, the amount of oxygen conveyed into the system is less in quantity, and calorification is diminished. They lessen the tonicity of the muscular fiber, by removing the irritation of the motor nerves. This is apparent from the general relaxation which follows their employment, and by the softened feel of the pulse at the wrist.
The primary influence of the proper stimulants is most undoubtedly exerted upon the cerebro-spinal system, but not thecase with sedatives; the influence of sedatives is not therefore antagonistic to, or the reverse of stimulants.
From what has already been stated, the therapeutical application of this class of remedies must be apparent; they are adapted to all cases of exalted organic action, inflammation, fever, etc. The excited heart, elevated temperature, hard and unyielding pulse, and the disordered state of the special senses, call for the administration of remedies fitted to appease their exalted energy; and such agents we have in the class we are now considering.
I. Action in Fever.—In fever of a sthenic character, accompanied with a high grade of reaction, both direct and indirect sedatives may be used with great advantage. The latter class of agents are in general use in such cases; thus we often administer emetics in nauseant doses, to produce their sedative influence during the febrile paroxysm; by them we produce a direct sedative influence upon the nervous centers, the action of the heart is lessened, the respiration is slower, and the muscular system is relaxed. Specific emetics, however, if given in nauseant doses, without producing vomiting, might with much propriety be classed with sedatives; they act upon the nerves as special sedatives, producing their nauseant and emetic effect, it is supposed, by their influence upon the pneumogastric nerve. Their beneficial effect in sedative doses, we suppose, is also exerted upon this nerve, and by this special sedation they lessen the action of the heart and lungs. The sedative action of these remedies, however, is partially antagonized by the reaction accompanying emesis.
Direct sedatives, as aconite, veratrum viride, etc., exert a like sedative effect to emetics, without, however, producing nausea, or the reaction produced by vomiting. By their action upon the nerves of the heart and lungs, they check the excited action of these organs, reduce the frequency of the pulse, and produce relaxation of the entire system. Thus, under the use of the two agents named, we have seen the pulse reduced from 130 beats in a minute to 70; the pulse would become soft and full, the system relaxed, and perspiration induced. If the effects of the remedy were permanent, there would be but little need of other medicine; but as the agents are neurotic, their effects are transitory, and without the agent is repeated, the advantage gained is soon lost.
The question might then arise, if their effects are so transient, what benefit will be gained by their administration? In the first place we prevent the progression of the disease until other remedies have had time to produce their remedial effects; we also induce a state of the system that is favorable for the operation of remedies generally considered to be curative. Thus we may easily produce diaphoresis when the system is thus relaxed, and by this means reestablish a normal secretion, and cause the elimination of any morbid material existing in the blood. Their action in this respect will be seen to be the more important, when we reflect that these diseases frequently arise from suppression of this secretion, and with what difficulty it is ordinarily reproduced in high grades of fever. The same remarks will apply to other secretions with the same propriety; for instance, the kidneys in fever do not eliminate from the blood their normal secretion; nor can we produce diuresis during high febrile excitement, without great difficulty; yet under the relaxing influence of one of these sedatives, the circulation is slower, and free diuresis can be easily produced.
Not only do they act as valuable auxiliaries in the treatment of fever, but they actually in many instances prove curative without any other treatment. Thus we have seen disease completely broken up, by keeping up their influence for twenty-four or thirty-six hours; under their relaxing and sedative influence the secretions became free, and the system, relieved of the high degree of excitement, in this time freed itself of the materies morbi which produced and kept up the febrile reaction. Nor are we alone in believing them to be curative agents, for many have witnessed similar effects, and there are probably none who have used the two agents named, but what have noticed them in some instances.
Compare the action of such an agent with the lancet, the great sedative agent of some practitioners, and we will clearly see the difference between sedation, produced by a nerve medicine, and that produced by exhausting the system of a fluid necessary to its existence. In the one case, the effect is temporary, a stoppage of nervous irritation; in the other, sedation is the result of exhaustion, produced by abstracting the nutritive fluid of the body.
II. Action in Pneumonia.—This class of agents are of especial importance in the treatment of acute inflammation of the lungs, for many reasons.
1st. They exert a marked control over the action of the heart, and by lessening its action they prevent the rapid influx of blood to the lungs, and thus prevent the progress of the inflammation. The greater the quantity of blood sent to them, the more dyspnoea must there be, the more venous blood passing into the arteries, as well as the more risk of effusion of lymph, and the obliteration of the cellular texture of the organ. If then we can arrest this determination, by the use of direct sedatives, which we can do, we arrest the main feature of the disease—in fact we stop the inflammatory action, and give the oppressed lungs time to recover from their morbid condition.
2d. They exert a direct action upon the pneumogastric nerve, calm its irritation, and through it exert a similar influence upon the inflamed tissue of the lung. By this action we diminish the sensation of want of breath, and thus do that for the lung which we do for the eye by darkening the room, or for an inflamed joint, when we prescribe absolute quiet—we do all we can to spare the exercise of the inflamed organ, which always aggravates the disease. By the same influence we check the harrassing cough, which invariably is accompanied with increaeed flow of blood to the lungs, and consequently increased congestion. The cough is checked, because the sensibility of the pneumogastric nerve is deadened, and it does not therefore convey to the brain the sensation of obstruction and irritation which exists in the lungs.
3d. They relax the entire system, and by lessening the rapidity of the circulation they relieve the excretory organs, and indirectly act as eliminatives. Thus, when the disease has arisen, as it may, from a morbid material in the circulation either introduced from without, or retained within the blood by the stoppage of an excretion, these agents produce that condition of the system which is favorable to its excretion.
From what has been said above, it will be evident that they are not only valuable as auxiliaries to other treatment, but they also act as direct curative agents. Especially is this the case in the first stage of the disease, for in this case they often stop the progress of the inflammation until the natural powers of the system remove the cause of the morbid process.
Indirect sedatives have long been used to fulfill the indications just described; thus we administer emetic agents in nauseant doses, to obtain their sedative effect upon the circulation, and because they diminish the sensibility of the lungs. By their use we prevent determination of blood to these organs, lessen their activity, check the cough, reduce the force and rapidity of the circulation, and produce general relaxation.
III. Action in Chronic Diseases of the Respiratory Apparatus.—This class of agents fulfill many indications in chronic diseases of the respiratory organs, in some cases being merely palliative, while in others they prove curative. In chronic bronchial inflammation and in phthisis pulmonalis, sedatives are valuable as palliatives, and even as curative agents. In these diseases, especially in the advanced stages, there is increased vascular action and nervous irritability, troublesome cough and hectic fever. The increased vascular activity, with the fixed irritation in the respiratory passages keeps up an undue afflux of blood to the lungs, the presence of which, connected with the increased rapidity of circulation, tends to irritate and excite the diseased organs, and keep up and even aggravate the cough; while the cough, in return, serves to increase the general excitement and pulmonic inflammation and hectic fever. In such cases the great desideratum is to moderate the momentum of the circulation by the use of sedatives, and to lessen the nervous excitability and irritability of the lungs and general system. Sedatives abate the incessant cough, moderate the hectic fever, and prove important sanative agents in curable cases, and equally important as palliatives in cases of an incurable character.
They are also used with much advantage in asthma, pertussis, and certain catarrhal affections; they allay the irritation and resolve the spasm upon which the cough is dependent, and often effectually relieve the complaint.
IV. Action in Inflammation of the Serous Membranes.—In this class of diseases, the agents we are now considering exert a prompt and marked curative influence. Wherever we have inflammation of a serous membrane, as in peritonitis, pleuritis, etc., we have a far greater excitemeut of the vascular and nervous systems, than when any other tissue is affected. Sedatives directly remove this excitement, allay the pain, and lessen the action of the heart; and by their influence in this respect, they rapidly lessen the inflammatory action. "Inflammation," says Dr. Ferguseon, "being made up of vascular and nervous action, of the afflux of blood to a part, and of pain, it is not irrational to act on both the elements of the malady at the same time, or in periods shortly consecutive of each other." By these agents we do act directly upon both; by lessening the force and frequency of the pulse, we check the vascular afflux to the inflamed part, and the medicine relieves the entire nervous system; we therefore strike directly at the foundation of the disease. Thus in peritonitis or pleuritis, by the administration of one of these agents, the veratrum viride, we may depress the action of the heart, lessen the pulse from 140 or 150 to 60 or 70 beats in the minute, relieve the severe pain, relax the system, promote the secretions, and by continuing the influence for twelve or twenty-four hours, the disease is entirely subdued.
In the first stages of puerperal peritonitis, or other forms of puerperal fever, they also exert a marked curative influence. In these cases it will not do to let the inflammation progress for twelve or twenty-four hours, while we are waiting for the action of the ordinary remedies. If we wish to cure our patient, it is necessary, in many instances, that the inflammatory process should be immediately arrested, or, at least, kept from progressing. Sedatives, in these cases, fulfill every indication; they check the afflux of blood to the inflamed part, lessen the fever, and quiet nervous irritability; and this influence we can continue as long as we may desire, by their use. If they do not prove curative in these cases, which we believe they do, they at least arrest the progrese of the disease until we can iufluence the system with other agents.
V. Action in Rheumatism.—This class of agents have proved to be very valuable in that species of rheumatism termed inflammatory. Its action in a case of this kind may be accounted for in the same manner as in true inflammatory diseases; it reduces the action of the heart, and thus prevents the afflux of blood to the diseased part; it deadens the sensibilities of the nervous system, and it produces relaxation of the entire system, and free action of the excretory organs. In these diseases, however, they should always be combined with or followed by such agents as will eliminate from the system the morbid material that has produced and kept up the disease.
Their most marked influence, however, is observed in cases of metastasis of the rheumatism to the heart. In these cases the symptoms are always very alarming, and not without cause, for it is probably the only fatal form of rheumatism. The principal symptoms of the disease, rapid pulse, palpitation, pain in the region of the heart, and extending up to the shoulder, difficulty of respiration, etc., would indicate a condition in which these agents might be successfully employed. And we find that under their use we can control the circulation, remove the pain and other symptoms, and radically remove the disease.
VI. Action in Disease of the Heart.—In hypertrophy, or in dilatation of the heart, in aneurism of any of the large arteries, in palpitation of the heart, ossification of the coronary arteries, aorta, etc., or in cases of ossification of the valves of the heart, the more frequent the systole and diastole of the organ, the more anxiety and suffering will the patient experience. Hence the importance of sedatives to allay the irritation existing, and reduce the frequency of the heart's action.
They are also beneficial in angina pectoris, a disease that usually owes its origin to organic heart disease. It has been found that the surest preventive against this disease is to avoid every thing that will accelerate the circulation, as attacks of it can always be traced to either mental excitement or muscular exertion, which has caused an increased action of the heart. Sedatives, by exerting a direct control over this organ, will prevent the excitement by which the paroxysm is produced, and many authors regard this class of agents as the most appropriate in the treatment of the paroxysms. Thus Dr. Elliston recommends hydrocyanic acid as the best agent; others belladonna, stramonium, etc.
VII. Topical Uses.—We have already stated, that these direct sedatives would produce the same effect upon the nerves with which they are brought in contact, that they would upon the nervous system when absorbed and conveyed to the nerves by the circulation. They thus become very useful in neuralgia, by the topical application to the part affected. In facial neuralgia, for instance, we often observe marked benefit from the topical application of the aconite; in some instances of very intractable cases, success has been reported by making an incision, or incisions into the part affected, and injecting the sedative agents into the wounds, bringing them into direct contact with the nervous trunks.
They are also used as topical agents in some conditions of the stomach. Thus, in nausea and efforts to vomit, arising from an irritation of the stomach, and not dependent upon morbid accumulation in it, sedatives calm the irritation, check the nausea, and stop the retching. In gastrodynia, pain or spasm of the bowels, or other local neuralgic affections, sedatives often give prompt and lasting relief.
1st. Sedatives are agents that act directly upon the nervous system, and relieves irritation. Their action is directly opposite to that of stimulants, and as they act upon the nerves their action is transient.
2d. They are useful in all diseases of an acute character, attended with acceleration of the pulse, from their marked effect in controlling the action of the heart.
3d. They are employed in fever, to lessen the action of the heart, lessen nervous irritability, and produce relaxation; by this influence they often prove curative agents.
4th. They prove beneficial in pneumonia, by lessening the action of the heart, time directly relieving the engorged lungs; by deadening the sensibility of the pneumogastric nerve, thus allaying cough, irritation and increased activity of these organs; by relaxing the entire system they equalize the circulation and promote secretion.
5th. They prove valuable in chronic disease of the respiratory organs, by lessening the irritation, checking the cough, and lessening the action of the heart.
6th. They are important curative agents, in the treatment of inflammation of the serous membranes, by directly contriving the essential parts of the process of inflammation, circulation and innervation.
7th. They are used with advantage in rheumatism, for the reasons above named; but they are of especial importance in this disease when it affects the heart, as by their use we may control the excitement of this organ. They are also important agents in the treatment of all diseases of the heart,—angina pectoris, aneurisms, etc.,—from the same reason.
8th. Their topical use is often beneficial in local neuralgic affections, gastrodynia, etc., as they exert the same effect upon the nerves of a part when applied locally, that they do upon the general nervous system, when conveyed to it by means of the circulation.
The American Eclectic Materia Medica and Therapeutics, 1898, was written by John M. Scudder, M.D.