What are the best medications for treating constipation?

Best Medications for Constipation

For general constipation, osmotic laxatives (polyethylene glycol 17g daily) or stimulant laxatives (senna or bisacodyl) are the preferred first-line medications, with PEG offering the best safety profile across all patient populations. 1

First-Line Medication Options

Osmotic Laxatives:

• Polyethylene glycol (PEG) 17g in 8 oz water once or twice daily is the optimal choice due to its excellent efficacy, tolerability, and safety profile, particularly in elderly patients 1, 2
• Lactulose is an alternative osmotic agent, though PEG is generally preferred 1
• Magnesium salts (magnesium hydroxide or citrate) are effective but must be used cautiously in renal impairment due to hypermagnesemia risk 1, 2

Stimulant Laxatives:

• Senna 2 tablets twice daily is the most cost-effective first-line option and does not require combination with stool softeners 2
• Bisacodyl 10-15 mg daily is equally effective as an alternative stimulant 1, 2
• Sodium picosulfate and cascara are additional stimulant options 1

Critical Medication to Avoid

Bulk laxatives (psyllium, methylcellulose, bran) should NOT be used in:

• Opioid-induced constipation 1
• Patients with reduced gastrointestinal motility (e.g., on anticholinergic medications like quetiapine or clozapine) 3, 4
• Non-ambulatory patients with low fluid intake (increased obstruction risk) 1

Docusate (stool softeners) alone are ineffective and should not be used as primary therapy 4

Escalation Strategy for Persistent Constipation

When first-line therapy fails:

• Increase bisacodyl to 10-15 mg two to three times daily before adding other agents 3, 2
• Add or switch to PEG if not already using it 3, 2
• Consider combining a stimulant with an osmotic laxative 1

Newer Prescription Agents

For chronic idiopathic constipation or IBS-C refractory to traditional laxatives:

• Linaclotide (guanylate cyclase-C agonist) is FDA-approved for IBS-C, chronic idiopathic constipation, and functional constipation in pediatric patients 6-17 years 5
• Lubiprostone 24 mcg twice daily (with food) is FDA-approved for chronic idiopathic constipation in adults 6
• Lubiprostone 8 mcg twice daily is approved for IBS-C in women ≥18 years 6

Special Population: Opioid-Induced Constipation

All patients on opioids require prophylactic laxatives from treatment initiation (unless pre-existing diarrhea) 1, 2:

• Start with senna 2 tablets twice daily or bisacodyl 10-15 mg daily 1, 2
• Add PEG 17g once or twice daily if constipation persists 2
• For laxative-refractory opioid-induced constipation: Methylnaltrexone 0.15 mg/kg subcutaneously every other day (contraindicated in bowel obstruction) 2
• Lubiprostone 24 mcg twice daily is FDA-approved for opioid-induced constipation in chronic non-cancer pain (not effective for methadone) 6

Rectal Interventions for Fecal Impaction

When digital rectal exam identifies full rectum or impaction:

• Glycerin suppository as first-line rectal intervention 4, 2
• Bisacodyl suppository 10 mg rectally once or twice daily as alternative 2
• Manual disimpaction with premedication (analgesic ± anxiolytic) if suppositories fail 4, 2
• Enemas are contraindicated in neutropenia, thrombocytopenia, recent pelvic surgery/trauma, or severe colitis 1

Key Safety Considerations

Before initiating or escalating treatment:

• Rule out bowel obstruction through physical examination and consider abdominal imaging if symptoms worsen 3, 4
• Assess for fecal impaction via digital rectal exam 3, 2
• Lubiprostone can cause nausea (take with food), diarrhea, and rarely syncope/hypotension 6
• Avoid liquid paraffin in bed-bound patients or those with swallowing disorders (aspiration pneumonia risk) 1

Elderly Patient Modifications

• PEG 17g daily offers optimal efficacy and safety in elderly patients 1
• Monitor for dehydration and electrolyte imbalances when using diuretics or cardiac glycosides concurrently 1
• Avoid saline laxatives due to hypermagnesemia risk 1
• Lubiprostone requires dose reduction: 16 mcg twice daily for moderate hepatic impairment (Child-Pugh B) and 8 mcg twice daily for severe impairment (Child-Pugh C) 6