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Emplastrum Picis Compositum.—Compound Tar Plaster.

Botanical name:

Related entry: Pix Liquida (U. S. P.)—Tar

SYNONYMS: Irritating plaster.

Preparation.—Take burgundy pitch, 24 troy ounces; white turpentine, 16 troy ounces; melt them together, add tar 48 troy ounces, stir well together and strain, remove from the fire, and add finely-powdered mandrake root, blood-root, poke-root, Indian turnip, each 10 troy ounces. Incorporate well together (T. V. Morrow). When it is desired to produce a more active preparation, and one which will act more promptly, euphorbium, in powder, 4 troy ounces, is added to the above.

Action and Medical Uses.—This plaster is irritant, rubefacient, and suppurative. It is used extensively in many cases where counter-irritation or powerful revulsion is indicated, in neuralgia, rheumatism, and in the majority of painful chronic diseases. It acts more efficiently, and is much more adhesive when spread quite thin, on soft leather, than when spread on any kind of cloth; though it may be spread on oil-silk, india-rubber cloth, or other substance that will not absorb any portion of it. This plaster may be held in place by a bandage or two, as it has to be removed daily, but when it is desired to have a firmer adhesion to the skin, some adhesive plaster may be applied around the margin left on the material upon which the tar plaster is spread. When applied to a part of the body, it must be removed daily, for the purpose of thinly respreading the same piece of leather, or oil-silk, etc., with the plaster, which is to be immediately reapplied upon the part. This course is to be continued until the surface, to which it is applied, commences discharging matter, after which it should be removed 2 or a times a day, wiping it quite dry each time before respreading it, and likewise carefully drying the sore as much as possible. This latter is best accomplished by lightly pressing upon it soft pieces of dry cotton, linen, or lint, so as to absorb all the pus. The practitioner must bear in mind that he is never, no matter what may be the condition of the sore or surrounding parts, to wet it; this will render it irritable and inflamed, and cause it to cease suppurating healthily, and even to require its immediate healing.

This plaster is very painful, producing more or less irritability of the system, and should never be used except when its use is indispensable; when it becomes very painful and irritating, depriving the patient of sleep, or causing him to complain loudly, it must be removed, and a slippery-elm poultice be applied. Many practitioners consider the disturbance of sleep, alone, as an indication for removing the plaster, which may be reapplied when it is desirable to continue the suppurative discharge for a longer time, as soon as the elm poultice has allayed the local irritation. If this is not required, the sore may be healed by some simple application, as simple cerate, a mixture of beeswax and tallow, red oxide of lead plaster, etc. Whenever the tar plaster or the dressing to the sore produced by it, are removed for renewal, the sore should each time be cleansed from matter in the manner referred to above. As the peculiar odor of the ingredients of this plaster may be observed in the excretions, there is no doubt but that they are absorbed into the system, and exert an alterative as well as a counter-irritating influence.


King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.



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