What is the appropriate senna dosing for an adult with occasional constipation (including maximum dose and treatment duration) and for children older than two years, and what are the contraindications and alternative laxatives?

Senna Dosing for Constipation

For adults with occasional constipation, start with senna 8.6–17.2 mg (1–2 tablets of 8.6 mg sennosides) taken once daily at bedtime, with a maximum dose of 30 mg daily (15 mL or 3 teaspoons of liquid formulation twice daily), and use for short-term relief or rescue therapy rather than continuous long-term treatment. 1, 2

Adult Dosing Algorithm

Starting dose:

• Begin with 8.6–17.2 mg (1–2 standard tablets containing 8.6 mg sennosides each) taken once daily at bedtime 1
• Most commercially available senna products contain 8–9 mg per tablet 1
• The FDA-approved liquid formulation dosing is 2–3 teaspoons (10–15 mL) once daily for adults 2

Maximum dose:

• Do not exceed 30 mg daily (approximately 3–4 tablets of 8.6 mg) 1
• FDA labeling specifies a maximum of 3 teaspoons (15 mL) twice daily for liquid formulations 2
• Critical pitfall: The 1 g daily dose studied in clinical trials is 10–12 times higher than typical therapeutic doses and caused dose reduction in 83% of participants due to abdominal cramping and diarrhea—avoid this excessive dosing 1, 3

Duration of treatment:

• Senna should be used for short-term or rescue therapy, not as continuous long-term treatment 1
• The American Gastroenterological Association conditionally recommends senna with the caveat that long-term effectiveness has not been studied 1
• While the single available trial lasted 4 weeks, longer-term use may be appropriate but requires periodic reassessment due to lack of safety data 1

Pediatric Dosing (Children ≥2 Years)

Age-specific dosing from FDA labeling: 2

• Ages 6–12 years: 1 to 1.5 teaspoons (5–7.5 mL) once daily; maximum 1.5 teaspoons (7.5 mL) twice daily
• Ages 2–6 years: 0.5 to 0.75 teaspoons (2.5–3.75 mL) once daily; maximum 0.75 teaspoon (3.75 mL) once daily
• Under 2 years: Consult a physician before use 2

Pediatric safety considerations:

• Senna is safe for long-term use in children with constipation, including those with anorectal malformations 4, 5
• Perineal blistering can occur (2.2% incidence) with high doses (≥60 mg/day) combined with prolonged stool-to-skin contact during nighttime accidents—advise frequent diaper changes 4
• No evidence of tolerance development exists in pediatric populations 4

Contraindications

Absolute contraindications: 1

• Intestinal obstruction or ileus
• Severe dehydration
• Acute inflammatory bowel conditions (active Crohn's disease, ulcerative colitis)

Pregnancy consideration:

• Sennosides are not recommended in pregnant women due to weak genotoxic effects observed in animal studies, though evidence remains controversial 1

Alternative Laxatives When Senna Fails or Is Contraindicated

First-line osmotic laxatives (preferred over senna for chronic use):

• Polyethylene glycol (PEG) 17 g daily is the strongest first-line recommendation with moderate-certainty evidence and superior long-term safety profile 1, 3, 6
• Lactulose 15–30 mL daily, though it has 2–3 day latency and may cause bloating 3
• Magnesium salts for rapid evacuation, but avoid in renal insufficiency due to hypermagnesemia risk 3, 7

Stimulant laxative alternatives:

• Bisacodyl 5–10 mg daily for short-term or rescue therapy; onset 6–12 hours orally, 30–60 minutes as suppository 1, 3
• Sodium picosulfate as an alternative stimulant 1, 3

Prescription secretagogues (second-line for refractory cases):

• Lubiprostone 24 mcg twice daily 1
• Linaclotide or plecanatide for patients unresponsive to over-the-counter agents 6
• Prucalopride as a prokinetic option 6

Clinical Algorithm for Escalation

1. Initial therapy: Start PEG 17 g daily OR senna 8.6–17.2 mg at bedtime 1, 3
2. If no response in 24–48 hours: Add bisacodyl 5–10 mg OR increase senna to maximum dose 3
3. If still constipated after 48 hours: Perform digital rectal exam to rule out impaction 3
4. If impaction present: Glycerin or bisacodyl suppository, then manual disimpaction if needed 3
5. If no impaction but persistent constipation: Consider small-volume enema or transition to prescription secretagogues 3

Common Pitfalls to Avoid

• Do not rely on docusate (stool softener) alone—it lacks efficacy evidence and is not recommended by major guidelines 3
• Avoid bulk laxatives (psyllium) for opioid-induced constipation—they are ineffective and may worsen symptoms 3
• Do not perform rectal interventions in neutropenic or thrombocytopenic patients due to infection and bleeding risk 3
• Start low with senna dosing—abdominal cramping and diarrhea are dose-dependent and common at higher doses 1