Recommended Dosage of Senna for Treating Constipation
The recommended initial dose of senna for treating constipation is 8.6-17.2 mg daily, with dosing adjustments based on symptom response and side effects. 1
Adult Dosing Guidelines
- For adults and children 12 years and over, start with 1 capsule (typically containing 8.6-9 mg sennosides) once daily, preferably at bedtime 2
- Maximum recommended dose is 2 capsules twice daily 2
- The dose evaluated in clinical trials (1 g daily) was higher than commonly used in practice, with 83% of participants reducing their dose during the trial due to side effects 1
- Titrate dose according to symptom response and side effects 1
- No clear maximum dose has been established in guidelines, though the recommended maximum is generally 4 tablets twice per day 1
Mechanism of Action and Timing
- Senna is a stimulant laxative derived from the senna plant 1
- Sennosides A and B are metabolized by gut microbiota to active metabolites (rheinanthrone and rhein) that stimulate prostaglandin E2 production and chloride ion secretion, increasing colonic peristalsis and water content 1, 3
- Onset of action is typically 6-12 hours, making bedtime administration preferable 2
- Antibiotics may decrease senna's efficacy by affecting the colonic bacteria that produce the active metabolites 1
Efficacy and Evidence
- Senna significantly increases complete spontaneous bowel movements (CSBMs) per week (MD 7.60,95% CI 5.90–9.30) compared to placebo 1
- Response rates are higher with senna compared to placebo (RR 5.25,95% CI 2.05–13.47) 1
- Quality-of-life scores may be higher in senna-treated patients compared to placebo (MD 7.80,95% CI 1.40–14.20) 1
- In loperamide-induced constipation, senna reduced colonic transit time from 39 ± 4 hours to 17 ± 3 hours (p < 0.005) 4
Side Effects and Precautions
- Common side effects include abdominal cramping, diarrhea, and abdominal pain, particularly at higher doses 1
- Perineal blistering is a rare side effect (2.2% in one pediatric study), associated with higher doses and prolonged stool-to-skin contact 5
- Senna is not recommended during pregnancy due to potential weak genotoxic effects observed in animal studies 1
- Contraindicated in individuals with ileus, intestinal obstruction, severe dehydration, or acute inflammatory conditions in the bowel 1
- Time-dependent effects have been observed, with optimal laxative effect after 7 days of administration in animal studies; prolonged use beyond 7 days may lead to diminished effect and slight colonic damage 3
Special Populations
- For children 6 to under 12 years: maximum 1 capsule twice a day 2
- For children under 6 years: consult a doctor 2
- In palliative care settings for patients with weeks to days of life expectancy, higher doses may be used: 2-3 tablets BID-TID with a goal of 1 non-forced bowel movement every 1-2 days 1
Duration of Treatment
- While clinical trials were conducted for 4 weeks, longer-term use is probably appropriate, though data on long-term tolerance and side effects are limited 1
- For chronic idiopathic constipation, the American Gastroenterological Association suggests senna over no treatment (conditional recommendation, low certainty of evidence) 1
- Some evidence suggests that senna should be used for less than one week to avoid diminished effect and potential colonic damage 3
Practical Considerations
- Senna is also present in many laxative teas, where dose may be difficult to calculate 1
- Over 90% of sennosides and their metabolites are excreted in the feces 1
- Senna is considered a safe treatment option for constipation in children when used appropriately 5
- Senna may be particularly effective in constipation related to anorectal malformation due to its stimulation of colonic propulsion waves 6