💊 MISCELLANEOUS AGENTS FOR CONSTIPATION

These meds don’t fit into laxatives, cathartics, or GC-C agonists, but they’re still very important for special cases like hepatic encephalopathy, opioid constipation, and IBS-C in women.

🧠 1. Lactulose (Constulose, Kristalose)

🔬 Class: Hyperosmotic agent / Synthetic sugar (disaccharide)

⚙ Mechanism of Action:

• Pulls water into the colon → softens stool

• Lowers colon pH by producing lactic + acetic acid

• Converts ammonia (NH₃) → ammonium (NH₄⁺) which gets trapped and excreted

• Constipation

• Hepatic encephalopathy → lowers blood ammonia!

🩺 Dosing

• Constipation: 10–20 g (15–30 mL) PO daily

• Encephalopathy: 20–30 g (30–45 mL) PO 3–4×/day, adjust to get 2–3 soft stools/day

• Enema: 300 mL lactulose + 700 mL saline/water

⚠ Adverse Effects

• Electrolyte imbalances

• Dehydration

• Gas, bloating, cramps

💡 Concept Mastery Tip:

💠 2. Lubiprostone (Amitiza)

🔬 Class: Chloride channel activator

⚙ Action:

• Activates chloride channels on intestinal cells → increases intestinal fluid secretion → stimulates motility

• Works locally, bypasses opioid suppression of motility

✅ Indications:

• Chronic idiopathic constipation (CIC)

• Opioid-induced constipation

• IBS-C in women ≥18 only (not studied in men!)

🩺 Dosage:

• CIC/Opioid constipation: 24 mcg PO BID with food

• IBS-C in women ≥18: 8 mcg PO BID with food

⚠ Adverse Effects:

• Nausea (especially in older adults) → take with food

• Severe diarrhea, dyspnea, hypotension, syncope

• Methadone may reduce effectiveness!

🚫 Avoid in:

• Pregnant women (limited data)

• Not approved for children

🧪 3. Sorbitol

🔬 Class: Hyperosmotic monosaccharide

⚙ Action:

• Pulls water into bowel via osmotic pressure

• Can be given orally or rectally

• Used with:

  • Sodium polystyrene sulfonate (Kayexalate) for hyperkalemia

  • Activated charcoal for poisoning

🩺 Dosage:

• PO: 30–150 mL of 70% solution

• Rectal enema: 120 mL of 25–30% solution

• Doses lower in children

⚠ Notes:

• Safe in pregnancy

• Monitor for diarrhea, dehydration

👩🏽 4. Tegaserod (Zelnorm)

🔬 Class: Serotonin (5-HT₄) receptor agonist

⚙ Action:

• Stimulates GI motility

• Used short-term for IBS-C in women <65 y

🩺 Dosage:

• 6 mg PO twice daily before meals

⚠ Adverse Effects:

• Headache, abdominal pain

• Serious: MI, angina, stroke, TIA

• Contraindicated in:

  • Moderate-severe renal or hepatic disease

  • Cardiovascular history

  • Women >65 y/o

🧠 Not a first-line drug due to serious risks.

👩‍⚕ 5. Prucalopride (Motegrity)

🔬 Class: Selective 5-HT₄ receptor agonist

⚙ Action:

• Stimulates normal GI peristalsis

• Used for chronic idiopathic constipation (CIC) in adults

🩺 Dosage:

• 2 mg PO daily

⚠ Contraindications:

• GI obstruction, ileus, perforation

• Severe IBD (Crohn’s, UC)

• Caution in kidney disease

😟 Adverse Effects:

• Diarrhea, nausea, abdominal pain

• Dizziness

• Suicidal ideation reported — Monitor for depression

📊 Quick Comparison Table

✅ NCLEX-STYLE QUESTIONS + RATIONALES

Q1: Patient Safety

Which of the following medications is contraindicated in a female patient over 65 years old with a history of transient ischemic attack?

• A. Lubiprostone

• B. Prucalopride

• C. Tegaserod

• D. Lactulose

✅ Answer: C. Tegaserod
Rationale:

• Contraindicated in women >65, and with TIA/stroke history

• A: Safe in older women

• B: Use with caution in kidney issues, but not specifically contraindicated

• D: No CV risks

Q2: Drug Matching

Match the medication to its most appropriate indication:

1. Lactulose

2. Lubiprostone

3. Sorbitol

4. Prucalopride

A. Chronic idiopathic constipation in adults
B. Treatment of hepatic encephalopathy
C. Potassium removal and constipation prevention
D. IBS-C in women

✅ Answers:

• 1 → B

• 2 → D

• 3 → C

• 4 → A

Q3: Adverse Effect Monitoring

A patient on lubiprostone reports dizziness and shortness of breath within 2 hours of taking their first dose. What should the nurse do first?

• A. Tell them to lie down and monitor BP

• B. Tell them this is normal and will go away in 24 hours

• C. Instruct them to take a second dose for relief

• D. Recommend stopping the medication immediately

✅ Answer: A. Tell them to lie down and monitor BP
Rationale:

• Acute dyspnea and hypotension are known effects — lie down, monitor vitals.

• May resolve before next dose.

📌 FINAL REVIEW TIPS:

• Lactulose:

  • Dual use: constipation + ↓ammonia

  • Traps NH₄⁺, lowers blood ammonia

• Lubiprostone:

  • For women only with IBS-C

  • Cl⁻ channel → fluid secretion

  • SE: Nausea, dyspnea, hypotension

• Sorbitol:

  • Given with Kayexalate or charcoal

  • Laxative + toxin remover

• Tegaserod:

  • IBS-C in females <65

  • Contraindicated in CV disease, renal/hepatic issues

• Prucalopride:

  • Good for CIC

  • Mental health risks: suicide ideation, dizziness