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.
Prickly Ash, Xanthoxylum Americanum, Northern Prickly Ash, and Fagara Clava-Herculis, Southern Prickly Ash. Official only in the United States. The name "fagara" has been dropped, and the spelling xanthoxylum changed to Zanthoxylum, thus following the recent works on botany.
The activity is probably due to an acrid resin which acts much like guaiac. See "Guaiacum." It is an aromatic bitter, sialogogue, and diffusible stimulant that acts reflexly, even to raising arterial tension.
A prompt diffusible stimulant probably not superior to capsicum. The fl. in 5-to 30- minim doses causes a warm glow and is prompt in relieving inert conditions of the gastro-intestinal tract. Given with other drugs, it promotes their absorption. Small doses given over a considerable period are reputed to be alterative and are employed in the treatment of chronic pharyngitis, lumbago, myalgia, and catarrhal jaundice.