How long should constipation last before considering lactulose and Sennakot (senna)?

Management of Constipation: When to Start Lactulose and Senna

Constipation should be treated after 2-3 days without a bowel movement, starting with stimulant laxatives like senna, and adding lactulose if constipation persists after 1-2 days of initial treatment. 1

Initial Assessment and Treatment Algorithm

Step 1: Identify and Address Constipation (Day 1-3)

• Assess for constipation when a patient has not had a bowel movement for 2-3 days
• Rule out impaction, especially if diarrhea accompanies constipation (overflow around impaction)
• Rule out obstruction through physical examination and abdominal radiograph if needed
• Treat other causes (hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus, medications)

Step 2: First-Line Treatment (Day 3-4)

• Start with a stimulant laxative: senna (Senokot) 8.6-17.2 mg daily 1
• Goal: One non-forced bowel movement every 1-2 days 1
• Monitor response for 1-2 days

Step 3: Add Second Agent if Needed (Day 5-6)

• If constipation persists after 1-2 days of senna treatment, add lactulose 30-60 mL twice to four times daily 1, 2
• The FDA-approved adult oral dosage for lactulose is 2-3 tablespoonfuls (30-45 mL) three to four times daily 2
• Adjust dosage every 1-2 days to produce 2-3 soft stools daily

Medication Details

Senna

• Mechanism: Stimulant laxative that increases bowel motility
• Initial dose: 8.6-17.2 mg daily (typically at bedtime)
• Maximum dose: Recommended maximum is 4 tablets twice per day 1
• Onset of action: 6-12 hours
• Side effects: Abdominal cramping, diarrhea

Lactulose

• Mechanism: Osmotic laxative
• Initial dose: 15-30 mL twice daily
• Can be increased to 30-60 mL 2-4 times daily as needed 1, 2
• Onset of action: 24-48 hours
• Side effects: Bloating, flatulence, abdominal discomfort

Special Considerations

For Opioid-Induced Constipation

• Opioid-induced constipation should be anticipated and treated prophylactically with a stimulant laxative 1
• If constipation persists despite senna and lactulose, consider adding methylnaltrexone 0.15 mg/kg subcutaneously every other day 1, 3

For Persistent Constipation

• If constipation persists despite senna and lactulose, consider:
  • Polyethylene glycol (1 capful/8 oz water twice daily)
  • Magnesium hydroxide (30-50 mL daily to twice daily)
  • Magnesium citrate (8 oz daily)
  • Phosphasoda or tap water enema until clear 1

Evidence Quality and Comparative Effectiveness

Studies comparing lactulose and senna have shown mixed results:

• Some older studies suggest lactulose may be more effective with fewer side effects in children 4
• Other research indicates that combination products containing senna may be more effective than lactulose alone in elderly patients 5
• The most recent guidelines from the National Comprehensive Cancer Network recommend a stepwise approach, starting with stimulant laxatives and adding osmotic agents if needed 1

Common Pitfalls to Avoid

1. Delayed treatment: Don't wait too long to initiate treatment; constipation becomes harder to treat the longer it persists
2. Inadequate dosing: Start with recommended doses and titrate as needed
3. Failing to rule out impaction: Always check for impaction before starting laxatives
4. Not addressing underlying causes: Identify and treat reversible causes of constipation
5. Overuse of stimulant laxatives: Senna is recommended for short-term use (4 weeks or less) 3

Remember that the goal of constipation management is to achieve one non-forced bowel movement every 1-2 days 1. Regular monitoring and dose adjustment are essential for effective management.