(From α, neg. and pain).
Anodynes are medicines which ease pain and procure sleep. They are usually divided into three sorts, viz.
1. Paregorica. mitigo, called also anetica. Paregorics, or such as assuage pain.
2. Hypnotica, Hypnopaeos. Hypnotics, or such as relieve by procuring sleep; somnus.
3. Narcotica. Narcotic, or such as ease the patient by stupifying him; stupefacio.
These divisions are not however correct, as there is no distinction between paregorics and hypnotics, except in degree; nor is there any evidence of the stupefa-cients acting differently from the latter: it would, at least, be a difficult task to ascertain where the one order begins, and the other ends. We would suggest a more natural and convenient division, viz. narcotics and in-irritants; the first to be again divided into opiates and stupefacients; the second into medicines which excite new motions, or those which remove sources of irritation. We thus include anodynes of every kind.
Though we cannot accurately discriminate between the opiates and stupefacients in their respective lists, where they approach near to each other, we can distinguish them in their extremes; and may instance, as examples, opium and hemlock. The opium, we know, is taken from the poppy; but its natural order, the rhaeades, affords no other medicine. The umbellate contain the hemlock and the dropwort; and the solanaceae plants of the strongest carcotic powers, solanum, digitalis, hyoscyamus, datura, and many others. From other classes of plants we find the wolf's bane, (aconi-rum napellus,) flammula Jovis, lactuca virosa, lauroce-rasus, prunus laurocerasis,) camphire, laurus cam-jihora,) agaricus muscarius, coculus Indicus, lolium temulentum, (l.spicis aristatis,) and the Indian hemp, cannabis sativa. Chemistry gives us the oil of wine, nitrous aether, wine, and ardent spirits. All these seem to act in a way somewhat similar; viz. on the nervous system through the medium of the stomach, and perhaps differ only in degree; for the hemlock and the henbane, in moderate doses, seem to produce easy and quiet rest.
What change is produced in the nervous system by these medicines, or the opposite class of stimulants, we cannot in this place determine, because it would anticipate the subject. We may however observe, that in animals styled cerebral by Virey, (see Animal.) the whole nervous system communicates with the head, and that the stomach is the organ by whose nerves the head is most readily affected. A small sedative power applied to a nerve, has little influence beyond the nerve itself, and the organ to which it is sent; but the same degree of activity exerted on the stomach, produces effects more extensive, which are soon communicated to the brain and the whole system. Of the change in the nerves from these medicines we know little. It is highly probable, that an active fluid, analogous to the electrical or Galvanic, gives them their peculiar power; that its activity is confined to the nervous fibril, which, in its minuter ramifications, is accompanied by a non-conducting sheath or coat. At the extremities only is the nervous fibril free from this impediment, and in the stomach are these extremities chiefly accessible. The power, then, whatever it be, in sedative substances, which occasions this diminished action, most powerfully affects those nerves, and is from their constitution immediately communicated to the brain, diminishing or destroying its functions.
The system of Dr. Brown has occasioned a considerable change in the language of pathology and therapeutics, by the distinction which he introduced between direct and indirect stimulants. In this place it is sufficient to hint at the difference of language, because it is apparently supported by stimulant powers which, in the greater number of anodynes, are at first obvious. It has been supposed by sounder physiologists, and more accurate observers, that these substances contain a stimulant with the sedative power, and that the former is more quickly exerted than the latter. This idea is not however very probable, both from the great dissimilarity of the two principles, and that the previous stimulant effects are disproportioned to the sedative, while many sedatives seem to produce no previous stimulus. Both in the arterial and nervous systems we have found great reason to suspect, that irregular action has been mistaken for increased action; and from the effects of sedatives, we very generally see irregular action only. This principle we shall have occasion to develop in explaining many parts of the animal economy. In the question before us we may instance the most common sedative, when in excess, because it is preceded by the most violent stimulating effects - we mean ardent spirits. While every artery in the body seems to act with increased energy; while the more violent passions are animated to phrcn-sy, the voluntary muscles are certainly weakened during its action. The other intellectual functions are no longer exercised. The mind and body, even in the moments of fury, lose in many respects their power. If we are rightly informed of the effects of the Indian intoxicating powers, even in the moments of phrensy, partial debility is apparent, and, in the action of opium, we find very quickly irregular wanderings of the mind, though sometimes accompanied with a quicker or somewhat fuller pulse; and, in general, it will be very difficult to discover in this latter medicine a real stimulating power. When we consider its use
S in inflammatory diseases, we shall show that it is seldom dangerous from its stimulus, The foxglove, and some others of the solanaceae, seem to have no stimulating effect: they are purely sedative, and act as such on the arterial and nervous system; but it is doubtful whether they are truly anodyne or hypnotic.
A tendency to sleep is constantly produced in situations where we cannot readily trace the cause; viz. after a full meal. Whether, in the process of digestion, some gas of a sedative nature is evolved; or whether, Ob former physiologists have supposed, the pressure of the stomach on the descending vessels occasions a greater flow of blood to the head, is uncertain. Each cause may have some influence. For this reason it is needless to observe, that anodynes should not be given after a full meal: they are at least unnecessary; yet custom has long established the innocence, if not the Utility, of the fumes of tobacco in such circumstances. The inirritants, the second class of sedatives, are as various as the causes of irritation they are designed to remove. Extraordinary action, in any part, is relieved by blisters and friction; and, in some instances, well managed conversation, by inspiring hope, confidence, or cheerfulness, will produce sleep. Mental irritation is also soothed by exciting a less distressing series of thoughts; by melodious strains; by light narratives; by repeating verses or numbers; by watching, in imagination, corn waving in the wind; or roving, in fancy, through well known streets and roads. All these produce new motions, and less active ones, so that natural sleep soon follows. The regular movement of a coach, and, not to speak indecorously, the drawling voice of a dull preacher, will have the same effect.
We remove irritation of the nerves by the use of the pediluvium; but for this purpose it should be long continued, and the water not very warm; at about 98° of Fahrenheit it may be continued for more than half an hour. Irritation of the stomach may be removed by drinking cold or warm water. The irritation of too pure an air may be avoided by sleeping in a lower or more marshy situation, abounding more with hydrogen: thus asthmatics sleep better in a less elevated spot; and hectic patients have certainly slept sounder in the neighbourhood of a stable. Vapours of nitrous aether, and of hops, scarcely belong to this head; but perhaps their powers have been greatly exaggerated. Cold has been considered as a cause of sleep: it is certainly a cause of death, beginning with torpor; but slight degrees of cold are highly inimical to rest. Nitre, which cools the system and checks inordinate circulation, seems sometimes to occasion sleep by this operation; and camphor, in a way less obvious, seems, in febrile cases, to act as an hypnotic.
A great inconvenience resulting from opiates is a languor and dizziness on the following morning, similar to what results from taking ardent spirits or wine in excess. In some cases the cicuta seems to act as an anodyne, without the same consequences; and a preparation of opium by a surgeon of Lancaster, appears to affect the head very slightly after its operation. This is partly owing to its being a watery, rather than a spirituous, solution; and a tincture from wine or weak spirit is scarcely inferior. The correctors of opium we must consider under that article. See Opium.