Definition. - The dried rhizome of Rheum officinale Baillon, Rheum palmatum L., and the var. tanguticum Max. or other species of Rheum, grown in China or Thibet, and deprived of most of the bark and carefully dried.

Description and Properties. - In cylindrical, conical, or flattish segments, deprived of the dark-brown, corky layer, smoothish or somewhat wrinkled, externally covered with a bright yellowish-brown powder, marked with white, elongated meshes, containing a white, rather spongy tissue, and a number of short, reddish-brown or brownish-yellow striae; compact, hard; fracture uneven; internally white, with numerous red, irregularly-curved, and interrupted medullary rays, which are radially parallel only near the cambium line; odor somewhat peculiar, aromatic; taste bitter, somewhat astringent. When chewed, rhubarb feels gritty between the teeth and imparts a yellow color to the saliva. Rhubarb which is very porous, or has a prominently mucilaginous taste, or is of a dark-brown color internally, should be rejected.

The drug contains the following constituents: chrysophan (and chrysophanic acid), emodin, imperfectly isolated glycosides as cathartin, or cathartinic acid, rheo-tannic acid, starch, calcium oxalate, etc.

Dose. - 5-30 grains (0.32-1,94 Gm.) [15 grains (1 Gm.), U. S. P.].

Official Preparations

Extractum Rhei - Extracti Rhei - Extract of Rhubarb. - Dose, 3-15 grains (0.19-1.0 Gm.) [4 grains (0.25 Gm.), U. S. P.].

Fluidextracium Rhei - Fluidextracti Rhei - Fluidextract of Rhubarb. - (This preparation is used in Mistura Rhei et Sodas and in Syrupus Rhei).

Dose. - 5-30 minims (0.3-2.0 Cc.) [15 minims (1 Cc), U. S. P.].

Pilulae Rhei Compositae - Pllulas (acc.) Rhei Compositas - Compound Rhubarb Pills. - Each pill contains about 2 grains (0.12 Gm.) of rhubarb, with purified aloes 1 1/2 grains (0.09 Gm.), myrrh, and oil of peppermint.

Dose. - 1 to 3 pills.

Pulvis Rhei Compositus - Pulveris Rhei Compositi - Compound Rhubarb Powder (Gregory's Powder).(25 per cent. with magnesia and ginger).

Dose. - 1/2-1 dram (2.0-4.0 Gm.) [30 grains (2 Gm.), U. S. P.].

Tinctura Rhei - Tincturae Rhei - Tincture of Rhubarb.(20 per cent., with cardamom).

Dose. - 1/2-4 fluidrams (2.0-15.0 Cc.) [1 fiuidram (4 Cc), U. S. P.].

Tinctura Rhei Aromatica - Tinctura Rhei Aromaticae - Aromatic Tincture of Rhubarb.(20 per cent., with cassia, cinnamon, cloves, and nutmeg).

Dose. - 1-3 fluidrams (4.0-12.0 Cc.) [30 minims (2 Cc.), U. S. P.].

This preparation is used to make Syrupus Rhei Aromaticus.

Mistura Rhei et Sodae - Misturae Rhei et Sodae - Mixture of Rhubarb and Soda. - Formula: Sodium bicarbonate, 35; fluidextract of rhubarb, 15; fluidextract of ipecac, 3; glycerin, 350; spirit of peppermint, 35; water, to 1000.

Dose. - 1/4-2 fluidounces (8.0-60.0 Cc.) [1 fluidram (4 Cc), U. S. P.].

Syrupus Rhei - Syrupi Rhei - Syrup of Rhubarb. - Formula: Fluidextract of rhubarb, 100; potassium carbonate, 10; spirit of cinnamon, 4; water, 50; syrup, to 1000.

Dose. - 1-4 fluidrams (4.0-15.0 Cc.) [2 fluidrams (8 Cc), U. S. P.].

Syrupus Rhei Aromeiticus - Syrupi Rhei Aromattici - Aromatic Syrup of Rhubarb. - Formula: Aromatic tincture of rhubarb, 150; potassium carbonate syrup, 850.

Dose. - 1/2-2 fluidrams (2.0-8.0 Cc.) [2 fluidrams (8 Cc), U. S. P.].

Physiological Action and Therapeutics. - Rhubarb in moderate doses is a stomachic, acting similarly to the aromatic bitters, increasing secretion, peristalsis, vascularity, and absorption, thereby aiding digestion and serving as a tonic. In larger doses it is a mild cathartic, producing in from four to eight hours a soft yellowish-brown evacuation, not watery, which is not infrequently accompanied by griping.

After full doses of rhubarb have been taken the purgative action is succeeded by quiescence of the bowels, the constipation being the result of the action of the astringent constituents of the rhubarb. Small doses, however, taken daily, serve a useful purpose in relieving habitual constipation without in the least impairing digestion.

The drug is excreted with the feces, urine, perspiration, and milk; the urine is slightly increased in amount and, together with the perspiration and milk, is colored yellow. The milk acquires a bitter taste and purgative properties.

Rhubarb is one of the best purgatives for children suffering from diarrhea caused by irritating ingesta in the bowels or to cold; it is also of value in some cases of dysentery. Summer diarrhea of children is often cured by some preparation of rhubarb alone, the diarrhea ceasing after a free purge by the drug.

As a simple laxative for children it is a valuable remedy, owing to its secondary tonic and astringent effects, and is recommended as a laxative to expel thread-worms.

When hemorrhoids are connected with constipation, much relief may be obtained by the gentle action of rhubarb.

Administration. - Rhubarb is seldom given alone, because of the griping it occasions. For children the syrups are excellent preparations, and the mixture of rhubarb and soda is an appropriate remedy when the secretions of the stomach and bowels are unduly acid.

In habitual constipation of adults the simple rhubarb pill is an efficient preparation.

The choice of the preparation will depend largely upon the individual case.