What is Senna used for in the treatment of constipation?

What Senna Is Used For

Senna is a stimulant laxative used to treat occasional constipation and chronic idiopathic constipation, typically producing a bowel movement within 6-12 hours. 1

Primary Indication

Senna relieves occasional constipation (irregularity) and is recommended by the American Gastroenterological Association-American College of Gastroenterology for adults with chronic idiopathic constipation (conditional recommendation, low certainty of evidence). 2, 3

Mechanism of Action

• Senna is derived from the senna plant and contains sennosides A and B, which are metabolized by gut bacteria into active metabolites (rheinanthrone and rhein) that stimulate prostaglandin E2 production and chloride ion secretion. 2, 3
• This mechanism increases colonic peristalsis and luminal water content, leading to bowel movements. 2
• Over 90% of sennosides and their metabolites are excreted in feces, making it safe for patients with chronic kidney disease. 3, 4

Dosing Strategy

• Start with 8.6-17.2 mg daily (typically one tablet at bedtime), which is the recommended initial dose. 3, 5
• Most commercially available senna products contain 8-9 mg per tablet. 2, 3
• Titrate upward only if inadequate response after several days, as higher doses increase risk of abdominal cramping and diarrhea. 3
• The dose used in clinical trials (1 g daily) was 10-12 times higher than standard practice, and 83% of participants reduced their dose due to side effects. 2, 3, 5

Clinical Efficacy

• Senna significantly increases complete spontaneous bowel movements per week (mean difference 7.60,95% CI 5.90-9.30) compared to placebo. 3
• Response rates are substantially higher with senna versus placebo (RR 5.25,95% CI 2.05-13.47), translating to 567 more responders per 1,000 patients treated. 2, 3
• Quality-of-life scores improve with senna treatment (mean difference 7.80,95% CI 1.40-14.20). 2, 3
• Senna demonstrated equivalent efficacy to magnesium oxide in a randomized controlled trial, with 69.2% response rate versus 11.7% for placebo. 6

Common Side Effects

• Abdominal cramping, diarrhea, and abdominal pain are dose-dependent side effects that typically resolve with dose reduction. 2, 3
• In pediatric populations, perineal blistering can occur (2.2% incidence) when high doses are used with prolonged stool-to-skin contact, particularly with nighttime accidents. 7
• No severe treatment-related adverse events occurred in clinical trials. 2

Duration of Treatment

• While clinical trials evaluated senna for 4 weeks, longer-term use is appropriate for chronic constipation management, though long-term safety data remain limited. 2, 3
• Senna can be used as first-line therapy or in combination with other agents like polyethylene glycol (MiraLAX). 5

Special Populations

Chronic Kidney Disease

• Senna is safe in CKD patients because over 90% is excreted in feces, unlike magnesium-based laxatives which should be avoided due to hypermagnesemia risk. 4

Palliative Care

• Higher doses (2-3 tablets twice to three times daily) may be used in palliative care settings with goal of one non-forced bowel movement every 1-2 days. 3

Pregnancy

• Senna is not recommended during pregnancy due to potential weak genotoxic effects observed in animal studies, though supporting evidence is controversial. 2, 3

Pediatric Use

• Senna is safe for long-term treatment of constipation in children, with no evidence of tolerance development. 7
• In children with anorectal malformations, senna is more effective than polyethylene glycol because it stimulates colonic propulsion without affecting stool consistency. 8

Contraindications

• Do not use in patients with intestinal obstruction, ileus, severe dehydration, or acute inflammatory bowel conditions. 3, 5

Important Clinical Considerations

• Antibiotics may decrease senna's efficacy by affecting colonic bacteria that produce the active metabolites. 3, 5
• Senna is available over-the-counter at low cost, making it an attractive first-line option. 2
• Senna is also present in many laxative teas where dose calculation may be difficult. 3
• Take at bedtime to allow the 6-12 hour onset of action to produce a morning bowel movement. 3

When to Escalate Therapy

If senna alone or combined with polyethylene glycol fails, consider bisacodyl 5-10 mg for short-term/rescue use, evaluate for fecal impaction, rule out mechanical obstruction, or consider prescription secretagogues (lubiprostone, linaclotide, plecanatide, or prucalopride) for refractory cases. 2, 5