The denuded and dried rhizome and roots of Rheum officinale, Baillon; Rheum palmatum, Linné, and var. tanguticum, Maximowicz, and probably other species of Chinese and Thibetan Rheum (Nat. Ord. Polygonaceae). Western and central portions of China and in Thibet. Dose, 5 to 30 grains.
Common Names: Rhubarb, Rhubarb Root.

Principal Constituents.—Chrysarobin (C35H26O7) (the yellow coloring glucoside, chrysophan or rhein) yielding chrysophanic acid (C15H10O4); the anthracene cathartic body emodin (C15H10O5); erythroretin, phaeoretin, aporetin, and the astringing principle rheotannic acid (C28H26O14); and quite a proportion of oxalate of calcium giving to rhubarb its grittiness.
Preparations.—1. Specific Medicine Rheum. Dose, 1/10 to 60 drops.
2. Syrupus Rhei, Syrup of Rhubarb. Dose, 1 to 4 fluidrachms.
3. Syrupus Rhei Aromaticus, Aromatic Syrup of Rhubarb. Dose, 1 to 4 fluidrachms.
4. Syrupus Rhei et Potassa, Compositus, Compound Syrup of Rhubarb and Potassa (Neutralizing Cordial). Dose, ½ to 4 fluidrachms.
5. Pulvis Rhei Compositus (Eclectic), Eclectic Compound Powder of Rhubarb. (Equal parts of powdered rhubarb, peppermint and bicarbonate of potassium). Dose, ½ to 2 drachms.
6. Pulvis Rhei Compositus, Compound Powder of Rhubarb (Gregory's Powder). (Rhubarb; Magnesium Oxide, and Ginger). Dose, 5 to 60 grains.
7. Beach's Neutralizing Mixture, Neutralizing Cordial, or Physic.—Take of rhubarb, pulverized, salaeratus, pulverized, peppermint plant, pulverized, equal parts. To a large teaspoonful add half a pint of boiling water; when cool, strain, sweeten with loaf sugar, and add a tablespoonful of brandy. (The original formula from Beach's American Practice.) Dose, 1 to 4 fluidrachms.
8. Locke's Neutralizing Cordial. (Formula.) Take of coarsely ground rhubarb, peppermint herb, and potassium bicarbonate, of each three ounces; boiling water, four pints; diluted alcohol, one pint; essence of peppermint, one-half ounce; white sugar, two pounds. Macerate the rhubarb, peppermint, potassium bicarbonate in the boiling water for two hours (do not boil) in a warm place. Strain and while still warm add the sugar; after the sugar is dissolved and the liquid is cold, add the diluted alcohol and the essence of peppermint (Locke). Dose, 1 to 4 fluidrachms. (We have found that by adding the potassium salt to the strained infusion of the rhubarb and peppermint a clearer preparation is obtained.)
9. Glyconda.—A sugarless preparation of Neutralizing Cordial, in which glycerin is the sweetening and preservative agent. Dose, 1 to 4 fluidrachms.

Specific Indications.—Gastric irritation, with elongated, reddened tongue, and nausea and vomiting; irritative diarrhea, with tenderness of abdomen on pressure; light-colored fecal discharges; gastro-intestinal irritation, with marked nervousness and restlessness, and screaming and convulsive muscular contractions. Sour-smelling discharges are relieved by small doses of neutralizing cordial or glyconda, while larger doses of either, or of specific medicine rheum or powdered rhubarb, are indicated for the relief of constipation with a sense of intestinal constriction and muscular contraction.

Action.—Rhubarb is stimulant to the gastro-intestinal tract, in sufficient doses increasing muscular contraction, and thus, rather than by increase of secretion, causing a cathartic action. This is probably due chiefly to the anthracene body, emodin. It affects the whole intestinal tract, especially the duodenum, and acts most certainly in the presence of bile, the secretion of which it probably promotes. The latter property, however, is still a point in dispute. Rhubarb usually purges in from four to eight hours and the stools are papescent and not watery, and of a yellowish-brown color (due to chrysophan). Their passage is attended with mild griping. The rapid absorption of the coloring matter imparts to the urine a yellow (if acid) or a carmine (if alkaline) color; the serum of the blood and mother's milk are stained yellow, and the sweat has a tawny hue. The cathartic effect of rhubarb is succeeded by a mild astringency due to the rheo-tannic acid, thus making the drug a calmative after a preliminary stimulating catharsis.

Therapy.—Rhubarb is an ideal laxative and cathartic according to the dose administered. In smaller amounts it is a gastro-intestinal stimulant and tonic, promoting the gastric secretions and insuring good digestion. As a laxative it is one of the best that can be used for children and women—specially the pregnant woman. As the evacuations produced by rhubarb are neither watery nor debilitating, when a tonic laxative is required for the feeble and for old people, rhubarb cannot be improved upon.

In severe febrile or inflammatory affections of the alimentary canal it is usually contraindicated, but where there are enfeebled digestion and irritation, or where food causes distress and irregular bowel action, either diarrheal or constipating, its use is attended with excellent results. Aromatics mitigate its griping tendency. In lienteric diarrhea, and where fecal accumulations are to be removed, and as a laxative following parturition, rhubarb is perfectly safe and effective.

In the summer diarrheas of children, when necessary to clear the intestinal canal of slimy, acid, or other irritating material, whether there is diarrhea or not, and there is both stomachic and intestinal indigestion, laxative doses of syrup of rhubarb, or the aromatic syrup or, preferable to either, the neutralizing cordial, have a most happy effect, and where other laxatives might leave an irritable condition and prolonged diarrhea, rhubarb, through its mild after-astringency, calms the excited intestinal tract. Sometimes castor oil, which also cleanses and afterwards checks the bowels, may be given with these preparations if so desired. For the constipation of dyspeptics, with hepatic torpor, it may be given with podophyllin or aloes; and in ordinary constipation it is sometimes effective if administered in pill with soap, which, in a measure, prevents its after-constringing effect. Ten-drop doses of specific medicine rheum in a glass of cold water, taken before breakfast, may be effective in overcoming constipation. Locke advises the following during convalescence from delirium tremens: Rx Rhubarb, Leptandra, Gentian, each 1 drachm; Ginger, 2 drachms; Diluted Alcohol, 16 fluidounces. Macerate. Sig.: Dose, One teaspoonful as required. Rhubarb is not a suitable agent where depletion is desired.

Rhubarb is an ideal summer gastro-intestinal remedy when not used as a laxative. It frequently is demanded in the practice of the specific medicationist to restrain bowel activity when the drug is administered in small doses. It thus controls diarrheal discharges due to gastro-intestinal irritation. When the tongue is red, long, narrow, and pointed, and the tip and edges reddened and the organ shows in its every fiber the signs of irritation—whether it be during summer complaint or in the papescent diarrhea of indigestion—it is a remedy of first importance. Here the dose should not exceed two grains of powdered rhubarb or two drops of specific medicine rheum every one-half or one hour until the character of the stools changes. An excellent medium for such conditions is the neutralizing cordial or, when sugar is contraindicated, glyconda may be substituted.

Neutralizing Cordial.—Neutralizing Cordial is one of the very best correctives yet devised for disorders of stomach and bowels, caused by overfeeding or change of water. It has three especial qualities: Rhubarb, through its specific adaptability to irritation of mucous surfaces, makes the cordial the ideal gastric sedative, for in such cases there is marked irritation, as shown by the reddened and pointed tongue. With most of these cases there is a fermentative state, with sourish and burning eructations, and often the bowel discharges contain sour and fermented material. For this condition there is no more pleasing antacid and corrective than potassium bicarbonate, though should the tongue show more pallor than redness, sodium bicarbonate may answer a better purpose. The aromatic qualities of the cordial derived from the peppermint oil and herb make it grateful as a carminative, and render it especially pleasant for children. Full doses (4 fluidrachms) act as a laxative, smaller doses as a corrective of irritation and acidity.

The physician who has not an intimate acquaintance with Neutralizing Cordial, or the Compound Syrup of Rhubarb and Potassa, has failed to realize the richness and fullness of the therapeutic allies handed down by the fathers of our school. This preparation has been prepared under various formulas, but as we have stated many times, we prefer that based upon Beach's original formula. That which we employ with greatest confidence is Locke's formula, which contains rhubarb, potassium bicarbonate, peppermint herb, peppermint essence, alcohol, and sugar. However, all of the preparations known as neutralizing cordial are of high order and possess similar properties. In sufficient dose, usually a tablespoonful, all of them are efficient agents to clear the intestines of undigested and irritating material. In Eclectic practice they have largely supplanted the use of such agents as castor oil. They are useful to cleanse the intestinal tract in indigestion, both gastric and intestinal-and in fermentative and irritative conditions of the stomach and bowels. The remedy should be given freely until the color of the stools shows the characteristic color of the medicine. Then to tone the bowels and allay irritation it may be continued in smaller doses at less frequent intervals. On the other hand, if the cathartic effects are not desired no remedy will be oftener indicated to control irritative diarrhea. Here the dose should not be larger than one drachm. Neutralizing Cordial finds a useful field in diarrhea of undigested aliment, in watery, copious diarrhea, in muco-enteritis, and in dysentery. Many physicians employ it as a vehicle for the administration of indicated remedies in stomach and bowel disorders. It is an ideal tonic to the stomach in the disorders of childhood, creates an appetite, and gives relief from pain and flatulence. The headache of indigestion, with sourish eructations, so common to children, is often cut short, as if by magic, by a laxative dose of Neutralizing Cordial. It is the most efficient remedy we have ever employed for diarrhea induced by change of drinking water and diet when travelling. Neutralizing Cordial is one of the best of the compounds handed down to us from early Eclectic pharmacy.

The representative sugarless substitute for neutralizing cordial is Glyconda, which many employ, not alone for the purposes named above, but as a vehicle for compatible medicines. For those who object to the presence of sugar in medicines, and particularly for those who are diabetically inclined, a glycerin preserved preparation has advantages. Where the tendency, even in the presence of the bicarbonate, is toward fermentation of the gastric contents, the glycerin preparation is sometimes to be preferred.

The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.