Castor oil is derived from Castor beans (Ricinus communis). The form of Castor oil used to treat medical conditions is known as Castor oil, USP.
The USP on Castor oil bottles is a medical acronym for United States Pharmacopoeia.
The United States Pharmacopoeia is a non-profit organization that determines safe standards for drugs as well as medical devices and diagnostics. USP publishes a compendium that clearly identifies standards for many drugs, including Castor oil.
Castor oil has been used since the time of the Pharaohs, and was one of the staples of traveling medicine men in the American West during pioneer days.
The Castor oil, USP used today for constipation meets stringent standards. It’s sometimes used as a bowel preparation to cleanse the intestines prior to diagnostic or surgical procedures.
Castor oil is a potent stimulant laxative that typically causes a bowel movement within five hours. Unlike less potent laxatives, it empties both the small and large intestines so thoroughly that you probably won’t have another bowel movement for two to three days.