What is the recommended dosing for ordering senna (laxative)?

How to Order Senna for Constipation

Start senna at 8.6-17.2 mg (1-2 tablets of 8.6 mg) once daily at bedtime, and titrate upward based on response, as most commercially available products contain 8-9 mg per tablet. 1

Initial Dosing Strategy

• Begin with 8.6-17.2 mg daily (equivalent to 1-2 standard tablets) taken at bedtime for adults with chronic idiopathic constipation 1
• The FDA-approved liquid formulation recommends 2-3 teaspoons (10-15 mL) once daily for adults, with a maximum of 3 teaspoons (15 mL) twice daily 2
• Start at the lower end of the dosing range and increase gradually if there is no response, as the 2023 AGA-ACG guidelines emphasize that trial doses (1 g daily) were significantly higher than typical clinical practice and 83% of trial participants reduced their dose due to side effects 3, 1

Dose Titration Algorithm

• Increase the dose incrementally every few days based on stool frequency and consistency until achieving 1 complete spontaneous bowel movement every 1-2 days 1
• If abdominal cramping or diarrhea occurs, reduce the dose immediately, as these side effects are dose-dependent 3
• No clear maximum dose is established in guidelines, though the general recommendation is up to 4 tablets twice daily (approximately 68-72 mg/day) 1
• In palliative care settings with limited life expectancy, higher doses of 2-3 tablets 2-3 times daily may be appropriate 1

Duration of Treatment

• While clinical trials evaluated 4-week treatment periods, longer-term use is appropriate for chronic constipation, though long-term safety data remain limited 3
• The 2023 AGA-ACG guidelines provide a conditional recommendation for senna use in chronic idiopathic constipation based on low certainty evidence 3
• Consider senna as first-line therapy or rescue therapy given its efficacy, low cost, and over-the-counter availability 3, 1

Critical Safety Considerations and Monitoring

Common pitfalls to avoid:

• Warn patients about perineal blistering risk with higher doses, particularly if prolonged stool-to-skin contact occurs (such as overnight incontinence episodes), as this occurred in 2.2% of pediatric patients at doses ≥60 mg/day 4
• Monitor for hypokalemia in patients on chronic therapy, especially those with cardiac conditions or taking QT-prolonging medications, as senna-induced diarrhea can cause significant electrolyte depletion 1
• Avoid in pregnancy due to potential weak genotoxic effects observed in animal studies, though supporting evidence is controversial 3, 1
• Contraindicated in ileus, intestinal obstruction, severe dehydration, or acute inflammatory bowel conditions 3, 1

Mechanism and Timing Considerations

• Senna's sennosides require bacterial metabolism in the colon to active metabolites (rheinanthrone and rhein), which stimulate prostaglandin E2 production and chloride secretion 3, 1
• Concurrent antibiotic use may reduce senna efficacy by disrupting colonic bacteria needed for activation 1
• Expect bowel movement within 6-12 hours of administration, which is why bedtime dosing is recommended 2

Evidence Quality Note

The recommendation for senna is based on a single small RCT from Japan showing significant increases in complete spontaneous bowel movements (mean difference 7.60 per week, 95% CI 5.90-9.30) and improved quality of life, though the certainty of evidence is low 3, 1