Senna - Drug Monograph

Introduction

Senna is a naturally occurring stimulant laxative derived from the leaves and fruits of several Cassia species, primarily Cassia senna and Cassia angustifolia. It has been used medicinally for centuries and remains one of the most widely used over-the-counter laxative products worldwide. Senna is classified as a stimulant laxative that acts directly on the intestinal mucosa and nerve plexus.

Mechanism of Action

Senna contains anthraquinone glycosides (sennosides A and B) that are hydrolyzed by colonic bacteria to active aglycone metabolites. These metabolites stimulate the myenteric plexus of the colon, increasing intestinal motility and inhibiting water and electrolyte absorption. The result is enhanced colonic peristalsis and decreased colonic transit time, typically producing a bowel movement within 6-12 hours after administration.

Indications

• Treatment of occasional constipation
• Bowel cleansing prior to diagnostic procedures (in combination with other agents)
• Management of constipation in specific patient populations (e.g., opioid-induced constipation, postpartum constipation)
• Prevention of straining in patients with cardiovascular conditions, hemorrhoids, or anal fissures

Dosage and Administration

• Take with a full glass of water
• Preferably administered at bedtime for morning evacuation
• Should not be used for more than 7 consecutive days unless directed by a healthcare provider
• Dosage adjustment may be necessary in hepatic impairment

Pharmacokinetics

Contraindications

• Known hypersensitivity to senna or any component of the formulation
• Acute abdominal pain including appendicitis
• Intestinal obstruction or ileus
• Severe abdominal pain, nausea, or vomiting
• Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis)
• Severe dehydration

Warnings and Precautions

• Not recommended for prolonged use (may lead to laxative dependence, cathartic colon, or electrolyte abnormalities)
• Use with caution in patients with electrolyte imbalances
• May cause abdominal cramping and discomfort
• Prolonged use may cause melanosis coli (benign pigmentation of colonic mucosa)
• Use with caution in patients with renal impairment due to potential electrolyte disturbances
• Not recommended during pregnancy unless clearly needed (Pregnancy Category C)

Drug Interactions

• May reduce absorption of other orally administered medications due to accelerated gastrointestinal transit
• Concurrent use with diuretics or corticosteroids may increase risk of hypokalemia
• May potentiate effects of cardiac glycosides in setting of hypokalemia
• May interact with other laxatives, increasing risk of excessive bowel activity

Adverse Effects

• Abdominal cramping
• Diarrhea
• Nausea
• Flatulence

• Electrolyte disturbances (hypokalemia, hypocalcemia)
• Discoloration of urine (yellow-brown to red)
• Melanosis coli with chronic use
• Laxative dependence with prolonged use

• Allergic reactions
• Stevens-Johnson syndrome (very rare)
• Hepatitis (case reports)

Monitoring Parameters

• Bowel frequency and consistency
• Electrolytes (especially potassium) with prolonged use
• Hydration status
• Signs of laxative abuse or dependence
• Abdominal discomfort or pain
• Urine color changes (educate patients about expected discoloration)

Patient Education

• Use only for short-term relief of constipation (not exceeding 7 days)
• Take at bedtime with a full glass of water for morning bowel movement
• Expect bowel movement within 6-12 hours after dosing
• Urine may turn yellow-brown or red; this is harmless
• Report severe abdominal pain, cramping, or rectal bleeding
• Increase fluid intake and dietary fiber while using senna
• Do not use if you have nausea, vomiting, or abdominal pain
• Not for long-term use without medical supervision
• Consult healthcare provider if constipation persists beyond 7 days

References

1. American Gastroenterological Association. (2013). Guidelines on the management of chronic constipation. Gastroenterology, 144(1), 211-217. 2. Müller-Lissner, S. A., et al. (2010). Myths and misconceptions about chronic constipation. American Journal of Gastroenterology, 105(11), 2328-2337. 3. FDA Drug Monograph: Senna. (2022). Over-the-Counter Laxative Drug Products. 4. Xing, J. H., & Soffer, E. E. (2001). Adverse effects of laxatives. Diseases of the Colon & Rectum, 44(8), 1201-1209. 5. World Health Organization. (1999). Monographs on selected medicinal plants: Senna leaf and pod. 6. Passmore, A. P., et al. (1993). A comparison of Agiolax and lactulose in elderly patients with chronic constipation. Pharmacology, 47(1), 249-252.