Lactulose

 

1. Generic & Brand Names

• Generic: Lactulose

• Brands: Duphalac®, Generlac®, Kristalose® (crystalline powder)

• Formulations:

  • Oral solution (10g/15mL)

  • Crystalline powder (10g, 20g packets)

  • No IV formulation

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2. Drug Class & Mechanism

• Class: Osmotic Laxative (Disaccharide)

• Mechanism:

  • Non-absorbable sugar → fermented by colonic bacteria → produces organic acids

  • Acids draw water into colon → softens stool + stimulates peristalsis

  • Lowers colonic pH → inhibits ammonia absorption (key for hepatic encephalopathy)

• Onset: 24-48 hours (constipation); 1-2 hours (hepatic coma)

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3. FDA-Approved Uses

Indication	Mechanism
Chronic Constipation	Osmotic laxative effect
Hepatic Encephalopathy	↓ Ammonia absorption via acidification
Off-label:	Small intestinal bacterial overgrowth (SIBO)

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4. Dosing Regimens

Indication	Adult Dose	Pediatric Dose (≥14 yrs)
Constipation	15-30 mL daily (10-20g)	10-15 mL daily
Hepatic Encephalopathy	30-45 mL TID-QID	Not established
Kristalose®	10-20g powder in 4oz water	10g daily
Administration Rules:

• Mix powder with water/juice

• Take with food to improve tolerance

• Titrate: Start low (15mL) → adjust to 2-3 soft stools/day

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5. Side Effects

Common (≥20%)	Serious (<1%)
Flatulence	Severe dehydration (excessive use)
Abdominal cramps	Electrolyte imbalances
Diarrhea	Hypernatremia (elderly)
Nausea	Lactic acidosis (rare)

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6. Contraindications & Warnings

• 🚫 Absolute Contraindications:

  • Galactosemia

  • Intestinal obstruction

  • Undiagnosed abdominal pain

• Use with Caution in:

  • Diabetes (contains galactose/fructose)

  • Electrolyte imbalances

  • Elderly (↑ risk hypernatremia)

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7. Drug Interactions

Medication	Risk	Management
Antacids	↓ Lactulose efficacy (neutralizes acid)	Separate by 2h
Non-absorbable Antibiotics	Synergistic for hepatic encephalopathy	Combine with rifaximin
Digoxin	Hypokalemia → ↑ toxicity risk	Monitor K⁺ levels

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8. Special Populations

Group	Recommendation
Pregnancy (Cat B)	Safe; preferred laxative
Lactation	Minimal absorption → safe
Children	Avoid <14 yrs for constipation*
Renal/Hepatic	No adjustment needed

*Used in infants for hepatic conditions under specialist care

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9. Efficacy Insights

• Constipation:

  70% patients achieve relief at 48h vs. 35% for placebo (Am J Gastroenterol)

• Hepatic Encephalopathy:

  Reduces recurrence by 50% vs. placebo when combined with rifaximin (NEJM)

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10. Storage & Handling

• Oral Solution: 15-30°C; avoid freezing

• Powder: Room temperature; protect from moisture

• Stability: Darkens over time → safe but bitter (replace if black)

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Clinical Practice Tips

✅ For Constipation:

• First-line for elderly/opioid-induced constipation

• Combine with docusate for stool softening

• Expect initial gas/bloating → improves in 3-5 days
  ❌ Avoid When:

• Acute abdominal pain (risk of perforation)

• Diarrhea already present

⚠️ Hepatic Encephalopathy Protocol:

Target: 2-3 soft stools/day
Underdosing → insufficient ammonia reduction
Overdosing → dehydration → worsens encephalopathy

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Lactulose vs. Other Laxatives

Parameter	Lactulose	Polyethylene Glycol (PEG)	Bisacodyl
Onset	24-48h	1-3h	6-12h
Safety	Safe long-term	Safe long-term	Avoid >3 days
Taste	Very sweet	Neutral	Bitter
HE Treatment	First-line	Ineffective	Ineffective

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Patient Counseling

1. "Expect delayed relief (1-2 days) – be patient!"

2. "Mix with juice/milk to improve taste."

3. "Titrate dose: Adjust until 2-3 soft stools/day."

4. "Report:

   • Severe cramps/distension

   • Watery diarrhea >3x/day

   • Confusion/lethargy (hepatic patients)"

💡 Pro Tip: For hepatic encephalopathy, use pH paper to verify stool pH <6.0 (confirms efficacy).

Prescribing Status: OTC in most countries.
Cost: Generic solution costs <$0.10/dose – preferred over branded products.

Sources: ACG Constipation Guidelines (2023), AASLD Hepatic Encephalopathy Guidelines (2022).