The root of Rheum palmatum.—Asia.
Preparations.—The powdered root. A tincture. Compound powder and compound syrup.
Dose.—Of the powder, gr. j. to grs. xxx. Of the tincture, gtt. j. to ʒss. Of the compound powder (an infusion of ℥ss. to ℥iv), one teaspoonful. Of the compound syrup, from gtt. x. to a tablespoonful.
Therapeutic Action.—Rhubarb is cathartic, astringent, tonic, and stomachic. In small doses it acts as an astringent tonic upon the digestive organs, promoting the appetite, and aiding digestion. It checks diarrhoea, and improves the condition of the alvine evacuations. It acts slowly and mildly as a purge, seldom causing any griping, and is often followed by constipation. It is said by some authors to aggravate febrile and inflammatory action in some cases. It renders the milk of the nurse purgative, and imparts to the secretions its yellow tinge. It may be said to occupy an intermediate position between tonics and drastic cathartics, in its mode of action.
As a cathartic, it is peculiar and highly important. Its peculiarity arises from its singular combination of properties; it is both cathartic and astringent, its cathartic action not seeming to be affected by its astringent influence. In addition to these properties, it is mildly tonic and stomachic.
As a cathartic, the rhubarb is not an active or efficient one, and yet it is of great value, and one for which we may search the materia medica in vain for a substitute. It is not important, nor is it a proper cathartic to be prescribed in the early stages of fever, or during high grades of febrile and inflammatory excitement; neither is it suitable for the treatment of dropsy. It does not deplete, but simply evacuates the bowels, without reducing the volume of circulating fluids by stimulating the intestinal exhalants; neither does it arouse the glandular system, restore the secretions generally, or equalize the circulation; hence it is unimportant in the early stages of the diseases to which reference is made. It is, however, of the first importance in another class of diseases, and even in the advanced stages of these mentioned. Its peculiar efficacy is conspicuous in dysentery, diarrhoea, cholera infantum, and in atonic states of the bowels—wherever the intestinal canal is in a relaxed or atonic state. In fevers of a typhoid type, in the advanced stages of all febrile and inflammatory diseases, after active purgation would be no longer admissible, this is an appropriate cathartic. It is also very useful in chronic disease, when there is debility of the system, and in those forms of dyspepsia attended with diarrhoea. In short, in all cases of general debility where cathartics are indicated, and in feeble and relaxed states of the bowels, this is one of our most valuable medicinal agents. It does not exhaust the energies of the general system, but invigorates them, while at the same time it evacuates the bowels by its action on the muscular coat, upon which writers suppose it to exert its principal influence.
It is often combined with prepared chalk and cinnamon, and administered in diarrhoea, especially in the treatment of children. In large doses it acts first as a cathartic, and secondly as a tonic and astringent. In small doses it acts as a laxative or aperient, and as a tonic or stomachic, and astringent.