What are the next steps for a patient with constipation who has not responded to Miralax (polyethylene glycol) and a bisacodyl suppository?

Management of Constipation After Failed Miralax and Bisacodyl Suppository

For a patient with constipation who has not responded to Miralax (polyethylene glycol) and a bisacodyl suppository, the next step should be trying a stimulant laxative such as oral senna or bisacodyl tablets, followed by consideration of newer agents like linaclotide if stimulant laxatives fail.

Step-by-Step Management Algorithm

1. Assess for Fecal Impaction

• Perform a digital rectal examination to rule out fecal impaction
• If impaction is present:
  • Consider glycerin suppository followed by mineral oil retention enema
  • Manual disimpaction may be necessary (with appropriate premedication) 1

2. First-Line Additional Treatments

Stimulant Laxatives

• Oral bisacodyl: Start with 5-10 mg daily (lower than the 10-15 mg used in trials to minimize side effects)

  • Take 30 minutes after a meal to enhance effectiveness 1
  • Common side effects include abdominal pain (24.7%) and diarrhea (53.4%) 1
  • Best used as short-term or rescue therapy due to side effect profile 1

• Senna: Start with 2 tablets daily, can increase to 2-3 tablets twice daily if needed

  • Effective for increasing bowel movements (7.6 more CSBMs per week vs placebo) 1
  • May cause abdominal cramping, especially at higher doses 1

3. If Stimulant Laxatives Fail (After 2-3 Days)

Try Different Osmotic Laxatives

• Magnesium hydroxide (Milk of Magnesia): 30-50 mL daily to twice daily
  • Avoid in patients with renal impairment 1
• Lactulose: 30-60 mL twice to four times daily 1
• Sorbitol: 30 mL every 2 hours for 3 doses, then as needed 1

4. For Persistent Constipation

Consider Newer Agents

• Linaclotide: 145 mcg orally once daily for chronic idiopathic constipation

  • Take on an empty stomach, at least 30 minutes before the first meal of the day 2
  • A lower dose of 72 mcg daily may be used based on individual tolerance 2
  • Diarrhea is the most common side effect (severe in 2% of patients) 2

• Lubiprostone: Consider if other options fail 3

5. For Opioid-Induced Constipation

• If the patient is on opioids, consider:
  • Methylnaltrexone: 0.15 mg/kg subcutaneously every other day 1
  • Naloxegol: Oral alternative to methylnaltrexone 3

Special Considerations

Combination Therapy

• Consider combining different classes of laxatives for synergistic effect
• Polyethylene glycol (PEG) and bisacodyl have distinct effects on colonic motility and may work well together 4
• PEG increases low-amplitude propagating contractions while bisacodyl increases high-amplitude propagating contractions 4

Evaluation for Underlying Disorders

• If constipation persists despite multiple interventions, consider:
  • Anorectal testing for defecatory disorders 1
  • Colonic transit studies if anorectal tests are normal 1
  • Pelvic floor retraining (biofeedback) for defecatory disorders 1, 3

Lifestyle Modifications

• Increase fluid intake
• Increase physical activity within patient limits
• Gradually increase dietary fiber intake 1

Pitfalls to Avoid

• Do not continue ineffective treatments for prolonged periods
• Do not ignore warning signs such as rectal bleeding, which may indicate serious conditions 3
• Avoid stimulant laxatives in patients with suspected intestinal obstruction 1
• Be cautious with magnesium-containing laxatives in patients with renal impairment 5
• Remember that antibiotics may decrease the efficacy of senna products as they affect the colonic bacteria that produce the active metabolite 1

By following this algorithm, you should be able to effectively manage constipation that has not responded to initial treatment with Miralax and bisacodyl suppository, improving patient comfort and quality of life.