Senna Dosing and Usage for Constipation
Start senna at 8.6-17.2 mg (1-2 standard tablets) once daily at bedtime, titrating upward based on response, with a goal of achieving one non-forced bowel movement every 1-2 days. 1, 2
Initial Dosing Strategy
- Begin with 8.6-17.2 mg daily (equivalent to 1-2 standard commercial tablets of 8.6 mg each) taken at bedtime 1, 2
- The FDA-approved liquid formulation contains 8.8 mg sennosides per 5 mL (1 teaspoon), with adults taking 2-3 teaspoons (10-15 mL) once daily 3
- Senna should be combined with polyethylene glycol (MiraLAX) 17 grams once daily as first-line therapy, as the American Gastroenterological Association recommends this combination approach 4
Dose Titration and Maximum Dosing
- Increase the dose gradually if inadequate response occurs, monitoring for cramping and diarrhea which indicate the need for dose reduction 4, 2
- The maximum FDA-approved dose is 3 teaspoons (15 mL) twice daily for liquid formulations 3
- Standard practice allows up to 4 tablets twice per day, though no clear maximum dose is established in guidelines 1
- In palliative care settings for severe constipation, doses may be escalated to 2-3 tablets two to three times daily 4, 2
Mechanism and Timing of Action
- Senna contains anthranoid compounds that require hydrolysis by colonic bacteria to become active, producing both motor stimulation of peristalsis and secretory effects 2
- Antibiotics may reduce senna's efficacy since gut bacteria are required for activation 4
- Take at bedtime to produce a bowel movement the following morning 3
Duration of Use and Safety Profile
- The American Gastroenterological Association recommends senna primarily for short-term use (4 weeks or less) or as rescue therapy 1, 2
- Long-term safety data are limited, though extended use may be appropriate in select cases such as palliative care 1, 2
- There is no convincing evidence that chronic senna use causes structural damage to enteric nerves, smooth muscle ("cathartic colon"), or increases colorectal cancer risk 5
- Senna is not carcinogenic in animal studies even at doses up to 300 mg/kg/day for two years 5
Common Side Effects and Management
- Abdominal cramping, pain, and diarrhea are the most common side effects, particularly at higher doses 1, 2
- Clinical trials using 1 gram daily (10-12 times higher than standard commercial tablets) resulted in 83% of participants reducing their dose due to side effects 4
- Perineal blistering can occur rarely (2.2% incidence) with higher doses (≥60 mg/day), prolonged stool-to-skin contact, or nighttime accidents—advise frequent diaper changes in non-toilet-trained children 6
- Prolonged or excessive use can cause electrolyte imbalances 1
Special Populations
- In chronic kidney disease, senna is safe with over 90% fecal excretion, making it preferable to magnesium-based laxatives 4
- Senna may be too strong for overtly weak or debilitated patients 2
- For children ages 6-12 years, use 1 to 1.5 teaspoons (5-7.5 mL) once daily; ages 2-6 years use 0.5 to 0.75 teaspoons (2.5-3.75 mL) once daily 3
- Consult a physician for children under 2 years of age 3
When to Escalate or Change Therapy
- If the MiraLAX-senna combination fails after appropriate titration, consider bisacodyl 5-10 mg for short-term or rescue use 4
- Evaluate for fecal impaction and rule out mechanical obstruction before escalating 4
- For refractory cases, consider prescription secretagogues such as lubiprostone (24 μg twice daily), linaclotide (72-145 μg daily), or plecanatide (3 mg daily) 1, 4
Quality of Life Benefits
- Senna significantly improves quality of life scores compared to placebo, with a mean difference of 7.80 points 4
- Response rates show 567 more responders per 1,000 patients treated with senna versus placebo 4