This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
In this condition, opium is often of great advantage, by diminishing the susceptibility of the nervous tissue of the part, and of the nervous centres, and thus obviating their injurious reaction upon the vascular tissue and the heart.
In nausea and vomiting from this cause, it is an admirable remedy, applied either by the stomach, the rectum, or endermically to the epigastrium; the two latter methods being resorted to, severally or conjointly, upon failure with the first. The subcutaneous exhibition also of the medicine is strongly indicated under these circumstances.
When any medicine has a tendency to irritate the stomach, this may generally be corrected by conjoining the medicine with a little opium, which is very much used for the purpose, and may always be employed unless when specially contraindicated. Thus, it may be given with nitrate of silver in chronic gastritis, and sulphate of copper in chronic enteritis; but should not generally be exhibited with cathartics, which it tends to counteract, nor with tonics in dyspepsia, because it rather weakens than invigorates the digestive function.
In slight diarrhoeas, resulting from vascular irritation, opium is often the only remedy required, when there is no indication for evacuating the bowels; and, when such an indication is offered by the presence of irritating matters, no remedy is so promptly effectual as fifteen or twenty drops of laudanum with a full dose of castor oil. In acrid poisoning, after the evacuation of the irritating agent both from the stomach and bowels, opium is the chief remedy required; and it may often be used advantageously in connection with the special antidote of the poison. Emetics and acrid cathartics frequently leave an irritation behind them, which is promptly relieved by opiates either by the stomach or the rectum. In irritations of the urinary and genital organs they are no less promptly useful, and often afford almost instant relief to great distress, as. for example, in the strangury from blisters. In these affections, the opium is most effectual when given by injection, or used as a suppository.
This exhibits itself in a great diversity of forms. which require a separate consideration.
Neuralgic pain is among the most frequent. Wherever this occurs, and under whatever name, opium is at least a most efficient palliative, sometimes absolutely indispensable from the suffering of the patient. Not unfrequently it will set the disease aside entirely for the time, especially when occurring periodically. Given so as fully to affect the system, it will often wholly supersede the paroxysm, and by thus breaking the chain of morbid association, effect at least a temporary cure. The quantity necessary to produce relief varies greatly with the violence of the pain, and the constitutional susceptibility of the patient. Sometimes an ordinary full dose will answer; but it will often be found necessary to double, triple, or quadruple it, before relief can be procured. When local application will answer the purpose, it should be preferred, as interfering less with the functions of the stomach and bowels. With the skin unbroken, little effect can generally be obtained; but, by means of the endermic method, or by injection into the subcutaneous areolar tissue, the medicine may generally be used with prompt and powerful effect, in the form of one of the salts of morphia. Not unfrequently a specially tender spot may be discovered in the track of the nervous trunk, supplying the painful part. In this case, the remedy should be applied to the point of tenderness; the cuticle having been first removed by a blister. But a great objection to the use of opium in neuralgia is the increasing dose in which it must be successively employed in order to procure relief, and the consequent danger of augmenting the quantity indefinitely, until the effects of the remedy become almost as pernicious as the disease itself. This objection applies especially to cases in which the affection is incessant in its attacks, and probably incurable. Yet the patient will seldom submit to severe suffering, when an agent of present relief is at hand; and the duty of the physician is so to regulate the remedy as to obviate its ill, and protract its beneficial effects as far as possible. This is to be done by allowing the dose to be increased only when absolutely necessary; by varying the surface of application between the stomach, the rectum, the skin, and the areolar tissue; by occasionally intermitting the use of the medicine, and endeavouring to obtain a similar effect by anodynes acting on different principles, as by chloroform or contain; and by correcting any resulting disorder of the functions by proper means, as constipation by laxatives, deficient action of the liver by mild mercurials or nitromuriatic acid, and enfeebled digestion by tonics, taking care not to do injury by the excessive use of the counteracting measures. By this plan, in incurable cases, the patient may be rendered more comfortable, and his life prolonged; whereas, if left to his own unrestrained propensities, he might soon exhaust the susceptibility of his system, and thus render the remedy almost useless.
Even in occasional attacks of neuralgia, occurring at considerable intervals, the physician should always bear in mind the danger of laying the foundation of an evil habit, and should guard the use of opiates with such precautions as may tend to obviate this result. Sometimes, in persons of feeble intelligence, or deficient power of self-control, it may be proper to disguise the medicine, so that the patient may not know what he is taking; and generally it is best to confine the use of opium, when the recurrence of the pain is frequent, to the severest attacks.
Besides the external attacks of neuralgia, which may occur in any sensitive part of the body, from the crown of the head to the joints of the great toe, there are various internal forms of it, which are sometimes even more imperious in their demands for relief as angina pectoris, gas-tralgia, enteralgia, nephralgia, and dysmenorrhoea, the last of which is, I believe, often nothing but a neuralgic form of rheumatism, and may be most effectually relieved by this anodyne given by the rectum. In nervous toothache and earache, opium may often be applied locally with effect; being introduced into a carious cavity, should a cavity exist, in the former case, and in a liquid form into the meatus externus, in the latter.