Treatment of Constipation
Start with a stimulant laxative (senna 2 tablets twice daily or bisacodyl 10-15 mg daily) as first-line therapy, aiming for one non-forced bowel movement every 1-2 days. 1
Initial Assessment Before Treatment
Before initiating any laxative therapy, perform a digital rectal examination to rule out fecal impaction or bowel obstruction 2. If impaction is present, suppositories and enemas become your first-line intervention rather than oral laxatives 2. Check for metabolic causes including hypercalcemia, hypokalemia, hypothyroidism, and diabetes mellitus 1. Review all medications and discontinue any non-essential constipating agents 2.
First-Line Pharmacological Treatment
Stimulant laxatives are the preferred initial therapy:
- Senna: 2 tablets twice daily 1
- Bisacodyl: 10-15 mg daily (can increase to 2-3 times daily if needed) 1, 3
The National Comprehensive Cancer Network guidelines explicitly recommend against adding stool softeners like docusate to stimulant laxatives, as evidence shows no additional benefit 1. This is a critical pitfall to avoid—many clinicians reflexively add docusate, but it provides no incremental value 1.
Alternative first-line option - Osmotic laxatives:
- Polyethylene glycol (PEG): 17g in 8 oz water once or twice daily 2, 3
- Lactulose: Takes 2-3 days to work; common side effects include sweet taste intolerance, nausea, and abdominal distention 2
- Magnesium salts: Use cautiously in renal impairment due to hypermagnesemia risk 2, 3
Both stimulant and osmotic laxatives are strongly endorsed in systematic reviews and are considered equally appropriate first-line options 2.
Supportive Lifestyle Modifications
Implement these measures alongside pharmacological therapy:
- Increase fluid intake to at least 2 liters daily 2, 1
- Increase physical activity within patient's limitations (even bed-to-chair transfers help) 2
- Ensure privacy and proper positioning (small footstool to assist gravity and straining) 2
- Schedule toileting attempts 30 minutes after meals, no more than 5 minutes of straining 2
Critical caveat about fiber: Dietary fiber requires adequate fluid intake (at least 2 liters daily) to be effective 1. Supplemental medicinal fiber like psyllium is unlikely to control medication-induced constipation and is not recommended in this context 1. Bulk laxatives are generally not recommended for opioid-induced constipation 2.
Second-Line Treatment for Persistent Constipation
If constipation persists after 1-2 weeks of first-line therapy:
- Add or switch to an alternative osmotic laxative (PEG, lactulose, magnesium hydroxide, or magnesium citrate) 1, 3
- Consider rectal bisacodyl suppository 10 mg once or twice daily 3
- Increase bisacodyl oral dose to 10-15 mg two to three times daily 3
Third-Line Treatment: Prokinetic Agents
If gastroparesis is suspected (particularly relevant with GLP-1 agonist use):
This is especially important in patients on medications that slow gastric emptying 1.
Fourth-Line Treatment: Secretagogues
For persistent constipation unresponsive to standard laxatives:
Linaclotide is FDA-approved for IBS-C and chronic idiopathic constipation in adults, with demonstrated efficacy in improving complete spontaneous bowel movements, stool consistency, and straining 5.
Management of Fecal Impaction
When digital rectal examination identifies a full rectum or fecal impaction:
- Glycerin suppository as first-line rectal intervention 3
- Bisacodyl suppository 10 mg rectally once or twice daily 3
- Manual disimpaction following premedication with analgesic ± anxiolytic 2, 3
- Mineral oil or warm water enemas 6
Critical contraindications for enemas: Do not use in patients with neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal or gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 2.
Special Considerations for Opioid-Induced Constipation
All patients starting opioids should receive prophylactic laxatives unless they have pre-existing diarrhea 2. Start the laxative with the first opioid dose 3.
- First-line: Osmotic or stimulant laxatives (same as above) 2
- Bulk laxatives like psyllium are specifically NOT recommended for opioid-induced constipation 2
- For laxative-refractory opioid-induced constipation: Methylnaltrexone 0.15 mg/kg subcutaneously every other day 3, 4
- Combined opioid/naloxone medications reduce the risk of opioid-induced constipation 2
- PAMORAs (peripherally acting mu-opioid receptor antagonists) may be valuable for unresolved cases 2
Critical warning: Do NOT use methylnaltrexone in patients with postoperative ileus or mechanical bowel obstruction 4.
Elderly Patient Considerations
Elderly patients require particular attention in assessment and treatment 2:
- PEG 17g/day offers excellent efficacy and safety profile in elderly patients 2
- Avoid liquid paraffin in bed-bound patients or those with swallowing disorders due to aspiration pneumonia risk 2
- Monitor closely for dehydration and electrolyte imbalances when using diuretics or cardiac glycosides concurrently 2
- Ensure toilet access, especially with decreased mobility 2
- Provide dietetic support and manage decreased food intake 2
Key Clinical Pitfalls to Avoid
- Do not add docusate to stimulant laxatives—no evidence of benefit 1
- Do not rely on fiber supplements alone for medication-induced constipation 1
- Do not use bulk laxatives without adequate hydration (at least 2 liters daily) 1
- Reassess for impaction or obstruction if constipation persists despite treatment 1
- Avoid long-term magnesium-based laxatives due to toxicity risk, especially in renal impairment 2, 6
Treatment Goals
Aim for one non-forced bowel movement every 1-2 days, not necessarily daily bowel movements 1, 3, 4. This is an important expectation to set with patients, as many believe daily bowel movements are required for normal function.