Castor Oil

Castor oil's primary fatty acid is ricinoleic acid. In the small intestine, lipases release ricinoleic acid, which activates EP3 prostaglandin receptors on intestinal smooth muscle. This produces strong peristaltic contractions and increased intestinal secretion, leading to laxation typically within 2 to 6 hours. For pharmaceutical use, modified castor oil derivatives serve as solubilizers in injectable and oral formulations. PEG-40 hydrogenated castor oil (Cremophor RH40, Kolliphor RH40) and polyethoxylated castor oil are common solubilizing agents. Topically, castor oil's high viscosity makes it a popular ingredient in skincare and hair products for conditioning, though clinical evidence for these uses is limited. The seed itself contains ricin, a highly toxic protein, but properly processed oil does not contain ricin.

Laxative use: 15 to 60 mL (1 to 4 tablespoons) as a single dose. Pharmaceutical excipient use: variable and controlled by formulation. Topical use: small amounts as needed.

Oral laxative: taken on an empty stomach in the morning; effect occurs in 2 to 6 hours. Plan accordingly. Topical: applied to skin or hair as desired.

Oral castor oil produces predictable, strong laxation. Side effects include abdominal cramping, nausea, dehydration, and electrolyte imbalance with overuse or chronic use. Not recommended for chronic constipation. Some people report skin sensitivity to topical application. Ricin contamination is not a concern in properly refined oil.

May reduce absorption of orally administered medications due to accelerated GI transit. Avoid concurrent use with other laxatives, diuretics, or potassium-affecting drugs to prevent dehydration and electrolyte loss.