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.
If, however, the application is continued too long, the cuticle separates, and an imperfect vesication takes place, which leaves behind a denuded and most painful surface, indisposed to heal kindly, and sometimes going on to suppuration. Ulceration also not unfrequently occurs under these circumstances, and sometimes gangrene, especially in children and patients with a feeble constitution and depraved blood. Such a result is to be particularly guarded against in scorbutic, malignant, and typhous affections.
In comatose conditions, there is great insusceptibility to the painful impression of mustard, as in cases of apoplexy and narcotic poisoning. Nevertheless, the application is not without effect. Sometimes the inflammation is obvious, though not sensible to the patient. in other instances, no apparent effect is produced during the prostrated state; but, on the occurrence of reaction, violent inflammation sets in, sometimes with very unpleasant consequences. in a case of poisoning from opium, in which, after the evacuation of the narcotic, the patient was left extremely prostrate, sinapisms were applied to the inside of the legs, and were allowed to continue for three hours, without the least apparent effect; the skin being in no degree reddened, and the patient quite insensible. Upon reaction, however, though the sinapisms had been long removed, the most violent inflammation came on, with an outline exactly corresponding with that of the application. This was followed by separation of the cuticle, ulceration, and suppuration; and it was long before the parts could be healed. This happened to me when a young practitioner, and was a useful lesson. I have never since allowed undiluted sinapisms to remain longer than three-quarters of an hour, or at furthest an hour, in contact with the skin.
Therapeutic Use. Mustard, externally used, is a most valuable medicine; and there are almost countless occasions for its employment. it may be resorted to in all cases, in which the indications are to rouse the system from a state of torpor, to stimulate it in sudden prostration, to divert from the head in congestive states of the brain, or to act re-vulsively from internal organs towards the surface, in neuralgic pains, violent spasm, or any other form of nervous derangement. The chills of malignant or pernicious fevers; the prostration from violent injuries; the collapse occurring in the course of fevers or other acute diseases; apoplexy, hemiplegia, coma, and convulsions of almost every variety; angina pectoris and dyspnoea; severe spasm of the stomach, bowels, bladder, etc.; gastralgia, enteralgia, and nephralgia; violent vomiting, cholera, and colic, are but a portion of the diseases, in which the external use of mustard is strongly indicated. When employed for a general impression on the system, or to divert from the brain, the sinapisms should for the most part be applied to the extremities; when for the relief of complaints of the chest or abdomen, immediately over the seat of the affection. Few remedies are more efficient in violent vomiting, and gastric spasm, than a sinapism to the epigastrium. Though less effective than blisters in internal inflammation, mustard may be employed when from any cause these remedies cannot be used. To recall retro-cedent gout and rheumatism, nothing perhaps is more effective than a sinapism applied to the former seat of the affection. But caution is necessary in the use of this remedy in any external disease, dependent on constitutional disorder. it should rarely be ventured upon in gout or rheumatism, seated in the muscles or the joints. I once knew death from violent pectoral disease, which apparently resulted from retrocession of lumbago, under the influence of a powerful local irritant to the back.
Application. Mustard is almost always applied in the form of cataplasm, to which, in reference to its active constituent, the name of sinapism is given. it should be prepared with cold water, and brought to a perfectly soft consistence, just short of diffluence. it is a mistake to mix mustard with vinegar or hot water, both of which tend to impair its efficiency. in my early practice, thinking to increase its activity, I on one occasion mixed it with alcohol, and was surprised to find no effect produced by it. The cause of this is now understood. When the sinapism is applied, its surface should be covered with gauze or extremely thin muslin, in order to prevent any portion from adhering to the skin when it is removed. Should a mild effect be required, it may be diluted with wheat or rye flour, or meal of Indian corn, in proportions to meet existing indications. When applied to children, or to the extremities of adults in diseases impairing the state of the blood, it should always be thus diluted, equal parts of the mustard and of the substance selected being ordinarily mixed together. But in severe affections of the stomach, bowels, and chest, it should be employed unmixed.
After the removal of the cataplasm, if the inflammation excited be considerable, simple cerate should be used as a dressing. if violent, it should be abated with dressings of cold water, or saturnine solutions. When a raw surface remains after the removal of the cuticle, Goulard's cerate is the best application
The volatile oil of mustard has been used as a rubefacient, 30 drops being dissolved in a fluidounce of alcohol, or 6 or 8 drops in a fluidrachm of olive oil. in this country, however, it is seldom if ever employed. M. Grimault prepares a sinapism by mixing three and a half drachms of glycerin, five drachms of starch, and twenty drops of the volatile oil of mustard; and M. Chevallier recommends a rubefacient plaster made by melting fifteen drachms of white pitch, and, after removing from the fire, mixing with it twenty drops of the volatile oil, and spreading on leather. (Am. Journ. of Pharm., xxxiii. 569.)