Senna Glycoside: Uses, Mechanism, and Safety for Constipation Relief
Senna glycoside, also known as sennoside or simply senna, is a medication primarily used to treat constipation and to clear the large intestine before surgical procedures or invasive rectal and colonic examinations. Derived from the Senna group of plants, this remedy has been utilized since at least the 700s AD and is recognized by the World Health Organization as an essential medicine.
As a stimulant laxative of the anthraquinone type, senna is available over-the-counter (OTC) in various forms, including tablets, liquids, granules, and rectal suppositories. It is widely recognized under brand names such as Ex-Lax and Senokot.
Key Facts
- Primary Use: Treatment of episodic and chronic constipation and bowel evacuation before surgery.
- Onset of Action: Minutes when administered rectally; 6 to 12 hours when taken orally.
- Drug Class: Stimulant laxative (anthraquinone derivative).
- Availability: Over-the-counter (OTC) in the US and Pharmacy medicine (P) in the UK.
- Common Side Effect: Abdominal cramping.
How Senna Works
The exact mechanism of action for senna is not entirely clear, but it is believed to function by increasing fluid secretion within the large intestine and stimulating contractions of the intestinal wall. Specifically, the breakdown products of senna act as irritants on the colonic wall, which induces motility and the secretion of fluids to facilitate a bowel movement.
Pharmacological Profile
Chemically, senna glycosides are dimeric glycosides and anthraquinone derivatives. With a molar mass of 862.746 g·mol and the chemical formula C42H38O20, these compounds are designed to target the colon directly.
Administration and Usage
Senna can be administered through two primary routes, each with a different onset time:
- Oral: Swallowed by mouth, typically producing a bowel movement within 6 to 12 hours.
- Rectal: Administered via suppositories, which can act within minutes or up to two hours.
While effective, senna is considered a weaker laxative compared to alternatives like castor oil or bisacodyl.
Safety, Contraindications, and Side Effects
While generally safe for short-term use, senna is not recommended for long-term application. Prolonged use may lead to electrolyte imbalances or impaired bowel function.
Contraindications
According to Commission E, senna should not be used in individuals with the following conditions:
- Intestinal obstruction.
- Acute intestinal inflammation (such as Crohn's disease).
- Ulcerative colitis.
- Appendicitis.
- Abdominal pain of unknown origin.
- Documented allergy to anthraquinones (though such allergies are rare and usually manifest as skin redness or itching).
Adverse Effects
The most common side effects are gastrointestinal, including nausea, vomiting, diarrhea, and abdominal cramps. Some users may notice that their urine turns a reddish color. A specific condition called melanosis coli—a brown pigmentation of the internal colonic wall—can occur with regular use and is visible during a colonoscopy.
Drug Interactions
Patients taking digoxin should exercise caution. Senna can reduce serum potassium levels, which may increase the toxicity and enhance the effects of digoxin.
Summary of Senna Glycoside
| Feature | Details |
|---|---|
| Chemical Class | Anthraquinone / Dimeric Glycoside |
| Common Brand Names | Ex-Lax, Senokot, Senna-Lax, Pursennid |
| Administration Routes | Oral, Rectal |
| Onset (Oral) | 6 to 12 hours |
| Onset (Rectal) | Minutes to 2 hours |
| Pregnancy Category | AU: A |
| Legal Status | OTC (US), Pharmacy (UK) |
Frequently Asked Questions
How long does it take for senna to work?
The timing depends on the method of administration. Rectal suppositories can work within minutes, while oral tablets or liquids typically take 6 to 12 hours to produce a bowel movement.
Can senna be used during breastfeeding?
While no harm has been found to result from the use of senna while breastfeeding, it is not typically recommended.
Is senna safe for children?
Senna is not typically recommended for use in children.
What is melanosis coli?
Melanosis coli is a characteristic brown pigmentation of the internal lining of the colon that can develop as a result of the regular, long-term use of senna products.
Can senna change the color of my urine?
Yes, it is possible for senna to change the color of urine to a somewhat reddish hue.