Recommended Dosage and Treatment Duration for Ex-Lax (Senna) for Constipation
For adults with constipation, the recommended initial dose of Ex-Lax (senna) is 8.6-17.2 mg (1-2 standard tablets) once daily, preferably at bedtime, with a maximum dose of 15 mL (3 teaspoons) twice daily. 1, 2
Dosage Guidelines
- The FDA-approved dosage for adults and children 12 years and older is 2-3 teaspoons (10-15 mL) once daily, not exceeding 3 teaspoons (15 mL) twice daily 2
- The American Gastroenterological Association recommends starting with a lower dose (8.6-17.2 mg daily, equivalent to 1-2 tablets) and increasing if there is inadequate response 1, 3
- Dosing should be adjusted based on symptom response and side effects 1
- Take senna at bedtime for optimal effect 2
Treatment Duration
- Clinical trials evaluated senna for 4 weeks, but longer-term use is likely appropriate for chronic constipation 4, 1
- The American Gastroenterological Association suggests senna for short-term use (4 weeks or less) or as rescue therapy, though longer use may be appropriate in some cases 3
- Data on long-term tolerance and side effects with extended use are limited 4, 3
Mechanism of Action
- Senna is a stimulant laxative that contains anthranoid compounds which are metabolized by gut bacteria to active metabolites 1, 3
- These active metabolites stimulate colonic peristalsis and increase water content in the colon 1
- Bowel movements typically occur 6-12 hours after administration 1
Side Effects and Precautions
- Common side effects include abdominal pain, cramping, and diarrhea, particularly at higher doses 4, 1, 3
- Abdominal cramping may occur with higher doses of senna 4
- Senna is contraindicated in individuals with ileus, intestinal obstruction, severe dehydration, or acute inflammatory bowel conditions 1
Special Considerations
- In palliative care settings, higher doses may be used: 2-3 tablets BID-TID with a goal of one non-forced bowel movement every 1-2 days 4, 1
- For chronic idiopathic constipation, the American Gastroenterological Association suggests senna over no treatment (conditional recommendation, low certainty of evidence) 4
- Antibiotics may decrease senna's efficacy by affecting the colonic bacteria that produce the active metabolites 1
Practical Tips
- Increase dose of laxative when increasing dose of opioids if treating opioid-induced constipation 4
- Maintain adequate fluid intake and dietary fiber intake while using senna 4
- If constipation persists despite optimal senna dosing, consider adding other laxatives 3
- The dose evaluated in clinical trials (1 g daily) was higher than commonly used in practice, with many participants reducing their dose during trials due to side effects 1