What are the recommended medications for a patient with constipation, considering their potential gastrointestinal disorders and other medications?

Recommended Medications for Constipation

Start with osmotic laxatives (polyethylene glycol or lactulose) or stimulant laxatives (senna or bisacodyl) as first-line pharmacologic therapy after ruling out impaction and obstruction. 1

Initial Assessment and Non-Pharmacologic Measures

Before initiating medications, assess for:

• Fecal impaction (especially if diarrhea accompanies constipation, suggesting overflow) 1
• Bowel obstruction via physical exam and abdominal x-ray 1
• Reversible causes: hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus 1
• Medication review: discontinue non-essential constipating drugs (anticholinergics, antacids, opioids) 1

Non-pharmacologic interventions should be implemented concurrently:

• Increase fluid intake 1
• Increase dietary fiber only if patient has adequate fluid intake and physical activity 1
• Encourage exercise when appropriate 1
• Ensure privacy, proper positioning, and scheduled toileting 1

First-Line Pharmacologic Options

Osmotic Laxatives (Preferred)

Polyethylene glycol (PEG): 17 g (1 capful in 8 oz water) daily, titrated per response 1

• Most cost-effective option ($10-45/month) 1
• Durable response over 6 months 1
• Common side effects: bloating, abdominal discomfort, cramping 1

Lactulose: 30-60 mL twice to four times daily 1

• Cost: <$50/month 1
• Only osmotic agent studied in pregnancy 1
• Bloating and flatulence may be limiting at higher doses 1

Magnesium hydroxide: 30-60 mL daily-twice daily 1

• Caution: Use cautiously in renal impairment due to hypermagnesemia risk 1

Magnesium citrate: 8 oz daily 1

Stimulant Laxatives (Alternative First-Line)

Bisacodyl: 10-15 mg daily to three times daily, targeting 1 non-forced bowel movement every 1-2 days 1

• Maximum 10 mg orally daily 1
• Can also use as suppository (one rectally daily-twice daily) 1

Senna: 8.6-17.2 mg daily (with or without docusate 2-3 tablets twice to three times daily) 1

• Evidence suggests docusate addition is unnecessary 1
• Maximum 4 tablets twice daily 1

Important caveat: Stimulant laxatives are recommended for short-term use or rescue therapy; long-term safety and efficacy are unknown 1

Management of Fecal Impaction

If impaction is identified:

• Glycerine suppository ± mineral oil retention enema 1
• Manual disimpaction following premedication with analgesic ± anxiolytic 1
• Tap water enema until clear 1

Contraindications for enemas: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, recent pelvic radiotherapy 1

Second-Line Options for Refractory Constipation

Intestinal Secretagogues

Lubiprostone: 24 μg twice daily 1

• Cost: $374/month 1
• Chloride channel activator 1
• May benefit abdominal pain 1
• Nausea is frequent side effect; diarrhea less common than other secretagogues 1

Linaclotide: 72-145 μg daily, maximum 290 μg daily 1

• Cost: $523/month 1
• Guanylate cyclase-C agonist 1
• Most efficacious secretagogue for IBS with constipation 1
• Diarrhea is common side effect 1

Plecanatide: 3 mg daily 1

• Cost: $526/month 1
• Another guanylate cyclase-C agonist 1
• Diarrhea frequency similar to linaclotide 1

Prokinetic Agents

Metoclopramide: 10-20 mg orally four times daily 1

• Consider when gastroparesis is suspected 1

Opioid-Induced Constipation (OIC)

All patients on opioids should receive prophylactic laxatives unless contraindicated by pre-existing diarrhea 1

First-Line for OIC

• Osmotic or stimulant laxatives (as above) 1
• Avoid bulk laxatives (psyllium) for OIC 1

Second-Line for OIC (Refractory to Standard Laxatives)

Methylnaltrexone: 0.15 mg/kg subcutaneously every other day, no more than once daily 1

• Peripherally acting μ-opioid receptor antagonist 1
• Preserves opioid-mediated analgesia 1
• Contraindications: postoperative ileus, mechanical bowel obstruction 1

Naloxegol: Similar peripherally-acting μ-opioid receptor antagonist studied for chronic opioid use 1

Alternative: Erythromycin for symptoms not responding to peripherally acting μ-opioid receptor antagonists 1

Common Pitfalls to Avoid

• Do not add fiber without adequate fluid intake and physical activity 1
• Do not assume diarrhea rules out constipation—check for overflow around impaction 1
• Do not use enemas in neutropenic or thrombocytopenic patients 1
• Do not use methylnaltrexone for postoperative ileus or mechanical obstruction 1
• Do not use magnesium salts in renal impairment 1
• Bulk laxatives are ineffective for opioid-induced constipation 1

Special Populations

Elderly Patients

• Ensure toilet access, especially with decreased mobility 1
• Provide dietetic support 1
• Manage decreased food intake (anorexia of aging, chewing difficulties) 1
• Educate to attempt defecation twice daily, 30 minutes after meals 1

Dying Patients (Weeks to Days Life Expectancy)

• Increase laxative ± stool softener dose (senna ± docusate 2-3 tablets twice to three times daily) 1
• Goal: 1 non-forced bowel movement every 1-2 days 1
• Consider hospice or specialized palliative care consultation if unacceptable symptom control 1