This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Rhubarb, Rheum species, universally official. R. officinale is a common designation. These - their several species - are Chinese Rhubarb. R. Rha-ponticum, official in France and Mexico, is European Rhubarb.
By reason of its contained chrysarobin, rhubarb imparts an orange-yellow color to the urine. Rhubarb slightly increases the flow of saliva; it is stomachic in moderate dosage and promotes digestion; it is purgative in larger doses. The drug possesses slight cholagogue effects. Owing to the rheotannic acid therein, the purgative influence of rhubarb is succeeded by constipation.
An exceedingly useful purgative; for, as has been said, "Rhubarb knows when to stop." With the bitters and alkalies, rhubarb should be used more commonly in the treatment of indigestion, especially with children. The aromatic syrup, combined with an alkali, is peculiarly efficacious in summer diarrhea. Diarrhea marked by intestinal relaxation and acrid secretion is a leading indication for rhubarb. As a laxative and purgative rhubarb is most valuable, but not especially so in chronic constipation, owing to its astringency.
The average dose is 15 grains; the fl. is given in 15-minim doses; the tr., used as a stomachic, in doses of 20 to 60 minims; the syrup and the aromatic syrup, average dose 2 fluidrachms; the extract, used in many pill formulae, 4 grains. The mixture of rhubarb and soda is given in an average dose of 1 fluidrachm.