What prn (as needed) medications for constipation should be prescribed for a post-operative patient with impaired bowel function (constipation) after Open Reduction Internal Fixation (ORIF) of a fracture at the base of the left femoral neck, currently on Docusate (stool softener) 250 mg daily?

PRN Medications for Post-ORIF Constipation

Add bisacodyl 10-15 mg orally daily as your first-line PRN agent, and consider polyethylene glycol (PEG) 17g in 8 oz water daily as an alternative or additional osmotic laxative. 1, 2

Why Docusate Alone is Insufficient

Your patient's current docusate 250 mg daily regimen is inadequate and likely ineffective:

• Docusate monotherapy fails in approximately 80% of postoperative orthopedic patients receiving opioids 3
• Multiple studies demonstrate that docusate provides no meaningful benefit over placebo for postoperative constipation 4, 5
• The American Gastroenterological Association strongly recommends traditional laxatives (stimulant or osmotic agents) as first-line therapy, with moderate-quality evidence 1

First-Line PRN Recommendations

Stimulant Laxatives (Preferred Initial Choice)

Bisacodyl:

• Dose: 10-15 mg orally daily PRN 1, 2
• Can be escalated to 10-15 mg two to three times daily if needed 2
• Works by stimulating colonic motility and reducing water absorption 1
• Goal: one non-forced bowel movement every 1-2 days 1, 2

Senna:

• Dose: 2 tablets (17.2 mg sennosides) twice daily PRN 1, 2
• Combination senna plus docusate showed superior efficacy to docusate alone in postoperative pelvic surgery (3.0 vs 4.05 days to first BM, p<0.002) 6
• However, senna alone (without docusate) was equally effective as senna plus docusate in hospitalized cancer patients 7

Osmotic Laxatives (Excellent Safety Profile)

Polyethylene Glycol (PEG):

• Dose: 17g (1 capful) in 8 oz water once or twice daily PRN 2
• Excellent safety profile with minimal systemic absorption 2
• Draws water into the gut to hydrate stool 1

Alternative osmotic agents:

• Magnesium hydroxide 30-60 mg daily-BID 1
• Lactulose 30-60 mL BID-QID 1
• Caution: Avoid magnesium-based laxatives if renal impairment present 2

Clinical Approach Algorithm

1. Rule out complications first (before prescribing any PRN laxatives):

   • Perform abdominal exam to exclude obstruction or impaction 1, 2
   • Consider abdominal x-ray if clinical concern for obstruction 1

2. Start with bisacodyl 10-15 mg PO daily PRN as your primary agent 2

   • This is the most evidence-based first-line choice for postoperative constipation 1, 2

3. Add PEG 17g daily PRN if bisacodyl alone is insufficient after 24-48 hours 2

   • Combining stimulant and osmotic laxatives is more effective than monotherapy 1

4. If no bowel movement after 2-3 days despite oral agents:

   • Glycerin suppository as first-line rectal intervention 2
   • Bisacodyl suppository 10 mg rectally once daily as alternative 1, 2

5. Escalate bisacodyl to 10-15 mg TID if persistent constipation 1, 2

Important Considerations for This Patient

Opioid use assessment:

• If patient is receiving opioids for pain control post-ORIF, prophylactic laxatives should have been started with the first opioid dose 2
• The AGA strongly recommends traditional laxatives as first-line for opioid-induced constipation 1

Mobility limitations:

• Post-ORIF femoral neck fracture patients have significant mobility restrictions
• Avoid bulk-forming laxatives (psyllium, methylcellulose) due to limited mobility and potential obstruction risk 2
• Encourage mobilization within physical therapy limitations 2

Fluid intake:

• Ensure adequate hydration to support laxative efficacy 1, 2

Common Pitfalls to Avoid

• Do not continue docusate monotherapy - it has proven ineffective in 79.9% of postoperative orthopedic patients 3
• Do not use methylnaltrexone in the immediate postoperative period - it is contraindicated for postoperative ileus 1, 8
• Do not delay treatment - 4 days without a bowel movement requires intervention now, not continued observation 1
• Do not assume stimulant laxatives cause colonic damage - there is little evidence supporting this widespread concern 1