How to manage constipation?

Management of Constipation

For adults with chronic idiopathic constipation, start with polyethylene glycol (PEG) 17g in 8 oz water once or twice daily as first-line pharmacologic therapy, which has moderate-quality evidence showing durable response over 6 months. 1

Initial Assessment

Before initiating treatment, perform a focused evaluation:

• Rule out bowel obstruction and fecal impaction through digital rectal examination (DRE) and abdominal examination 1, 2
• Obtain medication history to identify constipating agents that can be discontinued (opioids, anticholinergics, calcium channel blockers) 1
• Check for alarm symptoms: rectal bleeding, unintentional weight loss, sudden change in bowel habits 1
• Consider plain abdominal X-ray if severe fecal loading or obstruction is suspected clinically 1
• Check corrected calcium and thyroid function if clinically indicated 1

Stepwise Treatment Algorithm

Step 1: Lifestyle Modifications (Mild Constipation)

For patients with mild symptoms or dietary fiber deficiency:

• Increase fluid intake to at least 2 liters daily, particularly for those in the lowest quartile of fluid consumption 1
• Trial of fiber supplementation: Psyllium is the best-studied fiber, taken with 8-10 ounces of fluid per dose, up to 3 times daily 1, 3
• Increase physical activity and establish regular toileting habits after meals 1
• Ensure privacy and proper positioning (small footstool to assist with defecation) 1

Important caveat: Fiber supplementation has low-quality evidence and may cause flatulence and bloating. Studies are 30-40 years old with small sample sizes. 1 Bulk-forming laxatives like psyllium are unlikely to control opioid-induced constipation and should not be relied upon in that context. 1

Step 2: First-Line Pharmacologic Therapy

Polyethylene Glycol (PEG) is the recommended first-line agent:

• Dose: 17g (one capful) dissolved in 8 oz water once or twice daily 1, 2
• Evidence: Three randomized controlled trials show efficacy, with durable response over 6 months 1
• Side effects: Abdominal distension, loose stool, flatulence, nausea 1
• Safety profile: Excellent, with minimal systemic absorption 2

Alternative first-line option - Stimulant laxatives:

• Bisacodyl: 10-15 mg daily, can increase to 2-3 times daily if needed 2
• Senna with docusate: 2 tablets every morning, maximum 8-12 tablets per day 1, 2
• Goal: One non-forced bowel movement every 1-2 days 1

Step 3: Second-Line Agents (Persistent Constipation)

If PEG or stimulant laxatives fail after several days:

• Magnesium hydroxide: 30-60 mL daily (avoid in renal impairment due to hypermagnesemia risk) 1, 2
• Lactulose: 30-60 mL daily 1
• Sorbitol: 30 mL every 2 hours × 3, then as needed 1
• Magnesium citrate or additional PEG dosing 1

Before escalating therapy: Reassess for bowel obstruction and check for fecal impaction 1, 2

Step 4: Rectal Interventions

For refractory constipation or fecal impaction:

Suppositories:

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

Enemas (if oral treatment fails):

• Small-volume enemas: Sodium phosphate or docusate sodium enemas 1
• Large-volume enemas: Normal saline (1000 mL) or warm water enemas for impaction 1
• Oil retention enemas: For softening hard stool (hold 30+ minutes) 1

Manual disimpaction:

• Digital fragmentation and extraction following premedication with analgesic ± anxiolytic 1, 2
• Followed by enema or suppository, then maintenance oral regimen 1

Contraindications to enemas: Neutropenia, thrombocytopenia, recent colorectal/gynecological surgery, recent pelvic radiation, severe colitis, undiagnosed abdominal pain 1, 2

Step 5: Prokinetic Agents

For severe refractory cases:

• Metoclopramide: 10-20 mg PO 3-4 times daily 1

Special Consideration: Opioid-Induced Constipation

Prophylaxis is essential - constipation does not improve over time with opioids, unlike other opioid side effects 1

Prevention strategy:

• Start prophylactic laxatives with the first opioid dose 2
• Stimulant laxative + stool softener: Senna/docusate 2 tablets every morning 1
• Escalate laxative dose when increasing opioid dose 1
• Avoid relying on fiber supplements - they are ineffective for opioid-induced constipation 1

If standard laxatives fail:

• Consider opioid rotation to less constipating alternatives (e.g., transdermal fentanyl vs. oral morphine) 1
• Combination opioid/naloxone preparations reduce constipation risk 1
• Peripherally acting μ-opioid receptor antagonists (PAMORAs): Methylnaltrexone 0.15 mg/kg subcutaneously every other day for laxative-refractory cases 1, 2
• Naloxegol is another PAMORA option 1

Common Pitfalls to Avoid

• Do not use bulk-forming laxatives in patients with limited mobility or fluid intake - risk of obstruction 2
• Avoid long-term magnesium-based laxatives in renal impairment - risk of hypermagnesemia and toxicity 2, 4
• Do not perform enemas in neutropenic patients (WBC <0.5 cells/μL) - risk of bacteremia 1
• Stop laxatives and seek evaluation if: constipation lasts >7 days, rectal bleeding occurs, or no bowel movement despite treatment 3, 5
• Always rule out obstruction before aggressive laxative therapy 1, 2