What is the recommended dosage and usage of Senna (sennosides) for treating constipation?

Recommended Dosage and Usage of Senna for Constipation

The recommended initial dose of senna for treating constipation is 8.6-17.2 mg daily (equivalent to 1-2 standard tablets), with dosing adjustments based on symptom response and side effects. 1, 2

Adult Dosing Guidelines

• For adults and children 12 years and older, the FDA-approved dosage is 2-3 teaspoons (10-15 mL) of liquid senna once daily, with a maximum dosage of 3 teaspoons (15 mL) twice daily 3
• The typical starting dose for tablet formulations is 8.6-17.2 mg daily (1-2 standard tablets) 2, 4
• Dose should be titrated according to symptom response and side effects 2
• While no clear maximum dose has been established in guidelines, the generally recommended maximum is 4 tablets twice per day 2
• Taking senna at bedtime is often recommended for optimal effect 3

Mechanism of Action and Timing

• Senna is a stimulant laxative that contains anthranoid plant compounds which are hydrolyzed by colonic bacteria to yield active molecules 4
• It works by stimulating prostaglandin E2 production and chloride ion secretion, increasing colonic peristalsis and water content 2
• Antibiotics may decrease senna's efficacy by affecting the colonic bacteria that produce the active metabolites 2

Efficacy and Evidence

• Clinical trials have shown that senna significantly increases complete spontaneous bowel movements compared to placebo (MD 7.60,95% CI 5.90–9.30) 2
• Response rates are higher with senna compared to placebo (RR 5.25,95% CI 2.05–13.47) 2
• In a randomized controlled trial, senna (1.0 g daily) showed a 69.2% response rate for overall improvement of constipation symptoms compared to 11.7% with placebo 5
• Senna has been shown to improve quality-of-life scores compared to placebo (MD 7.80,95% CI 1.40–14.20) 2

Side Effects and Precautions

• Common side effects include abdominal cramping, diarrhea, and abdominal pain, particularly at higher doses 2, 4
• In clinical studies, approximately 10% of patients reported cramps and up to 27% experienced diarrhea 6
• Senna is not recommended during pregnancy due to potential weak genotoxic effects observed in animal studies 2
• Senna is contraindicated in individuals with ileus, intestinal obstruction, severe dehydration, or acute inflammatory conditions in the bowel 2
• Prolonged or excessive use can cause diarrhea and electrolyte imbalance 1

Special Populations

• In palliative care settings for patients with severe constipation, higher doses may be used: 2-3 tablets BID-TID with a goal of 1 non-forced bowel movement every 1-2 days 2, 4
• For children, dosing should follow age-appropriate guidelines as established by the FDA 3:
  • 6 to 12 years: 1 to 1½ teaspoons (5 to 7.5 mL) once daily, maximum 1½ teaspoons twice daily
  • 2 to 6 years: ½ to ¾ teaspoons (2.5 to 3.75 mL) once daily, maximum ¾ teaspoon once daily
  • Under 2 years: Consult a doctor

Duration of Treatment

• The American Gastroenterological Association recommends senna for short-term use (4 weeks or less) or as rescue therapy 4
• While clinical trials were typically conducted for 4 weeks, longer-term use may be appropriate in some cases, though data on long-term tolerance and side effects are limited 2
• For chronic idiopathic constipation, the American Gastroenterological Association suggests senna over no treatment (conditional recommendation, low certainty of evidence) 2

Practical Considerations

• Senna is also present in many laxative teas, where dose may be difficult to calculate 1, 2
• Over 90% of sennosides and their metabolites are excreted in the feces 2
• When using higher doses, patients should be advised about the risk of perineal skin irritation from prolonged stool contact with skin 7
• Consider adding other laxatives if constipation persists despite optimal senna dosing 4