Recommended Dosage and Usage of Senna for Constipation
The recommended starting dose of senna for treating constipation in adults is 8.6-17.2 mg daily (equivalent to 1-2 standard tablets), with dosing preferably at bedtime. 1
Adult Dosing Guidelines
- The American Gastroenterological Association (AGA) recommends a starting dose of 8.6-17.2 mg daily for adults with chronic idiopathic constipation 2, 1
- FDA-approved dosing for adults and children 12 years and older is 2-3 teaspoons (10-15 mL) of liquid formulation once daily (equivalent to 17.6-26.4 mg sennosides), with a maximum dose of 3 teaspoons (15 mL) twice daily 3
- Each 5 mL (1 teaspoon) of liquid senna contains 8.8 mg of sennosides 3
- Senna should be taken at bedtime for optimal effect, as its onset of action is typically 6-12 hours 2, 3
Mechanism of Action
- Senna contains sennosides A and B that are metabolized by gut bacteria to active compounds (rheinanthrone and rhein) 2, 1
- These active metabolites stimulate colonic peristalsis and increase chloride ion secretion, leading to increased water content in the colon 2, 1
- Similar to other stimulant laxatives, antibiotics may decrease senna's efficacy by affecting the colonic bacteria that produce the active metabolites 2
Dose Titration and Duration
- The AGA suggests starting at a lower dose and increasing if there is inadequate response 2, 1
- While clinical trials used higher doses (1 g daily), this is higher than typically used in clinical practice, and 83% of participants in studies reduced their daily dose during trials 2
- Most commercially available senna tablets contain 8-9 mg of sennosides per tablet 2
- The recommended maximum is 4 tablets twice per day 2
- For persistent constipation, doses may be increased up to the maximum recommended dose before considering adding other laxatives 1
Side Effects and Precautions
- Common side effects include abdominal pain, cramping, and diarrhea, particularly at higher doses 2, 1
- In a clinical trial with higher doses, side effects were common but most occurred in the first week of treatment 2
- Senna is contraindicated in individuals with ileus, intestinal obstruction, severe dehydration, or acute inflammatory conditions in the bowel 2
- Rare side effects include perineal blistering, particularly with higher doses (60 mg/day) and prolonged skin contact with stool 4
- Prolonged or excessive use can potentially cause electrolyte imbalance 2
Duration of Treatment
- The AGA recommends senna for short-term use (4 weeks or less) or as rescue therapy 1, 5
- While clinical trials were conducted for 4 weeks, longer-term use may be appropriate in some cases, though data on tolerance and side effects with extended use are limited 2, 1
- Recent research suggests that senna should be used in regular dosages for less than one week for optimal effect without colonic damage 6
- A comprehensive study showed that senna's laxative effect reached its peak after 7 days of administration and then diminished with continued use 6
Special Considerations
- Senna is classified as a stimulant laxative with conditional recommendation and low certainty evidence for treating chronic idiopathic constipation 5
- In the treatment algorithm for chronic constipation, senna is not a first-line agent; polyethylene glycol (PEG) is recommended as first-line therapy 5
- For patients with cancer-related constipation, higher doses may be required (2-3 tablets BID-TID) 1
- A comparative study showed that senna alone was more effective than senna plus docusate in hospitalized cancer patients 7
- When combined with psyllium (a fiber supplement), senna provides enhanced laxative effect compared to psyllium alone 8
Practical Tips
- Monthly cost of senna treatment is typically less than $50, making it an affordable option 2
- Senna is also present in many laxative teas, where dose may be difficult to calculate 2
- For optimal results, ensure adequate hydration while taking senna 1
- To avoid perineal skin irritation, maintain good hygiene and promptly clean the area after bowel movements 4