Scientific Name: Rheum palmatum
- Anthraquinones (emodin, sennosides A-F: rheinanthrone & rhein)
- Volatile oil
- Flavonoids (rutin)
- Fatty acids
- Calcium oxalate
- Cholagogue (Hepatic Stimulant)
- Laxative (stimulant)
Mechanism of Action & Pharmacology:
- Anthraquinones are absorbed into the blood and re-secreted into the colon as active anthraquinones, where they stimulate smooth muscle contraction.
- Sennoside metabolites (rheinanthrone & rhein) activate intestinal macrophages to significantly increase PGE2 concentrations and decrease the expression of aquaporin-3 (AQP3) expressed in the mucosal epithelial cells of the colon, which is involved in inhibiting water transport from the luminal to the vascular side, leading to a laxative effect.
- Emodin has been shown to inhibit ATP-induced IL-1β secretion, ROS production and phagocytosis attenuation in peritoneal macrophages.
- Volatile oils lend antispasmodic effects which help mitigate gripping associated with laxative use.
- Note: Laxative action is dose dependent
Safety & Toxicity Concerns:
- Adverse effects include acute intestinal pain and cramping (can often be offset with carminatives), and high doses may cause diarrhea with mild griping, icterus and hepatic enlargement, renal insufficiency and proteinuria.
- Use > 10 days consecutively can lead to dependence on laxatives for a bowel movement to occur.
- Recurrent use or abuse can lead to electrolyte imbalances (particularly hypokalemia), dehydration, and muscle and kidney destruction with hematuria and albuminuria.
- Harmless reddish/yellow discolouration of urine and feces may occur.
- May cause pseudomelanosis coli (PMC), a reversible deposition of active anthraquinone glycosides in the colon. Long term use may predispose to colon cancer.
- Avoid in pregnancy, lactation, intestinal obstruction, spastic constipation, acute intestinal inflammation, abdominal pain of unknown origin, and children <12 years old.
- Use caution in fever and with kidney stones.
- Due to decrease in transit time, may potentially interfere with absorption of practically any medication.
- Avoid concomitant use with potassium-depleting agents (e.g. thiazide diuretics, corticosteroids(Glycyrrhiza glabra), as may cause hypokalemia.
- May affect activity of cardiac glycosides & antiarrhythmic agents if potassium deficiency resulting from long-term laxative abuse is present.