What is the recommended dose of Senna (sennoside) for treating constipation?

Senna Dosing for Constipation

Start with 8.6-17.2 mg (1-2 tablets) of sennosides daily, taken at bedtime, and titrate upward based on response, with a typical maximum of 4 tablets twice daily (approximately 34.4 mg twice daily). 1, 2

Standard Adult Dosing

• Initial dose: 8.6-17.2 mg daily (equivalent to 1-2 standard tablets containing 8.6 mg sennosides each), taken at bedtime 1, 2, 3
• Maximum dose: Up to 4 tablets twice per day (total of 8 tablets daily, or approximately 68.8 mg/day), though no absolute maximum is established in guidelines 1, 4
• For liquid formulations: Adults start with 2-3 teaspoons (10-15 mL) once daily, with a maximum of 3 teaspoons (15 mL) twice daily 3
• Each teaspoon (5 mL) of liquid contains 8.8 mg sennosides 3

Dose Titration Strategy

• Adjust dose based on symptom response and side effects rather than using a fixed schedule 1, 2
• In clinical trials, 83% of participants reduced their dose from the studied 1 g daily due to side effects, indicating that lower doses are typically better tolerated 1
• The goal is to achieve one non-forced bowel movement every 1-2 days without causing diarrhea or cramping 4
• When increasing opioid doses in patients, simultaneously increase the laxative dose to prevent worsening constipation 4

Special Population: Palliative Care

• For patients with severe constipation in palliative care settings (weeks to days of life expectancy): 2-3 tablets two to three times daily (17.2-25.8 mg per dose) 1, 2
• This higher dosing range (up to 8-12 tablets daily total) may be necessary for opioid-induced constipation in cancer patients 4
• Target one non-forced bowel movement every 1-2 days 1, 4

Critical Timing and Administration

• Take at bedtime for optimal effect, as senna typically works within 6-12 hours 3
• Senna requires metabolism by gut bacteria to active compounds (rheinanthrone and rhein), so antibiotics may reduce efficacy 1
• Ensure adequate fluid intake to enhance effectiveness and prevent dehydration 4

Common Pitfalls to Avoid

• Do NOT add docusate sodium to senna—it does not improve efficacy and may actually reduce effectiveness 4, 5
• In a direct comparison study, sennosides alone produced more bowel movements than sennosides plus docusate (62.5% vs 32% had bowel movements >50% of days in symptom control patients, p<0.05) 5
• Avoid prolonged use at high doses without monitoring—doses above 60 mg/day are associated with increased risk of perineal blistering, particularly with nighttime accidents and prolonged stool-to-skin contact 6
• Do not continue ineffective dosing without escalation—if constipation persists after 2-3 days at current dose, increase the dose rather than adding docusate 4

Side Effects and Monitoring

• Abdominal cramping and diarrhea occur particularly at higher doses and typically resolve with dose reduction 1, 2
• Common side effects (13% of patients): abdominal cramping, vomiting, or diarrhea during initial weeks 6
• Monitor for hypokalemia with chronic use, especially in patients on QT-prolonging medications or with cardiac conditions, as severe diarrhea can cause life-threatening electrolyte depletion 1
• Perineal blistering is rare (2.2% in one pediatric series) but occurs with high doses (>60 mg/day) and prolonged stool contact with skin 6

Duration of Treatment

• While clinical trials evaluated 4 weeks of use, longer-term treatment is appropriate for chronic constipation, though data on extended use are limited 1, 2
• No evidence of tolerance development was found in systematic reviews 6
• For chronic idiopathic constipation, the American Gastroenterological Association suggests senna over no treatment (conditional recommendation, low certainty evidence) 1

Contraindications

• Absolute contraindications: ileus, intestinal obstruction, severe dehydration, or acute inflammatory bowel conditions 1
• Not recommended during pregnancy due to potential weak genotoxic effects in animal studies 1
• May be too strong for overtly weak or debilitated patients 2

When to Escalate Therapy

• If constipation persists despite maximum senna dosing (8 tablets daily), assess for fecal impaction or obstruction 4
• Consider adding bisacodyl or osmotic laxatives (not docusate) as next step 4
• For opioid-induced constipation unresponsive to standard therapy, consider methylnaltrexone 0.15 mg/kg subcutaneously 4