Lactulose

Lactulose: A Comprehensive Guide to Uses, Benefits, Dosage, Side Effects, and More

Lactulose is a widely prescribed osmotic laxative and ammonia-lowering agent used worldwide to treat chronic constipation and hepatic encephalopathy (a serious brain complication of liver disease). Known by brand names like Duphalac, Constulose, Enulose, Kristalose, Generlac, Cephulac, and many generics, lactulose is a synthetic disaccharide derived from lactose. 

Lactulose

It's on the World Health Organization's List of Essential Medicines and remains a first-line treatment in global guidelines (including AASLD, EASL, and NHS recommendations as of 2025-2026).

This article covers everything you need to know about lactulose from how it works to safe usage tips  based on the latest evidence from sources like NCBI StatPearls (updated 2024-2025), Cleveland Clinic, Drugs.com, and international hepatology guidelines.

What Is Lactulose and How Does It Work?

Lactulose (chemical name: 1,4-β-galactoside-fructose) is a non-absorbable sugar made of galactose and fructose. Unlike regular sugars, it passes through the small intestine unchanged and reaches the colon, where gut bacteria ferment it.

Key mechanisms of action

Osmotic effect: Draws water into the intestines → softens stool and promotes bowel movements (ideal for constipation).

Colon acidification: Fermentation produces lactic, acetic, and formic acids → lowers colon pH → converts ammonia (NH₃) to non-absorbable ammonium (NH₄⁺) → reduces blood ammonia levels (critical for hepatic encephalopathy).

Prebiotic benefits:

Supports beneficial gut bacteria (e.g., Bifidobacterium, Lactobacillus) while reducing harmful ammonia-producing ones.

Cathartic effect: 

Increases stool frequency and transit speed, flushing toxins.

This dual action makes lactulose unique — it's not just a laxative but a targeted therapy for liver-related brain issues.

Primary Uses of Lactulose

Chronic Constipation

Relieves long-term or occasional constipation by increasing stool water content and frequency.

Safe for adults, elderly, children, and long-term use when titrated properly.

Hepatic Encephalopathy (HE) / Portal-Systemic Encephalopathy

Treats and prevents brain dysfunction in liver cirrhosis or failure (e.g., from hepatitis, alcohol, NAFLD).

Lowers ammonia to reverse symptoms like confusion, sleep changes, tremor, or coma.

Often combined with rifaximin for prevention of recurrent episodes (reduces recurrence by ~50-60% per guidelines).

Other off-label or emerging uses include gut microbiome support, though constipation and HE remain the main indications.

Recommended Dosage (Adults – 2025-2026 Guidelines)

Dosage varies by condition and should always be guided by a doctor. Aim for 2-3 soft bowel movements per day.

Constipation

Starting dose: 15-30 mL (about 10-20 g) once or twice daily.

Adjust as needed (up to 60 mL/day). Effects in 24-48 hours.

Hepatic Encephalopathy:

Acute/initial: 30-45 mL every 1-2 hours until 2 bowel movements occur, then maintenance.

Maintenance: 30-45 mL, 3-4 times daily (or 20-30 g equivalent).

For rapid relief: 

Rectal enema (300 mL in 700 mL water/saline, retained 30-60 min) if oral not possible.

Children: 

Lower doses (e.g., 5-20 mL twice daily for ages 5-17); pediatric use requires doctor supervision.

Take with water/juice; start low to minimize side effects. Titrate based on stool consistency.

Side Effects and Precautions

Lactulose is generally safe and well-tolerated, but common issues include:

Common (often temporary): Bloating, gas (flatulence), abdominal cramps, gurgling, nausea.

If over-dosed: Diarrhea, dehydration, electrolyte imbalance (e.g., low potassium).

Rare/Serious: 

Worsening confusion in HE if not monitored, hypersensitivity.

Precautions:

Avoid in galactosemia (galactose intolerance).

Use caution in diabetes (contains small fructose), bowel obstruction, or severe diarrhea.

Pregnancy/breastfeeding: 

Usually safe (Category B), but consult a doctor.

Interactions: 

Antibiotics may reduce effectiveness (kill gut bacteria); monitor with other laxatives.

Side effects often improve within days — reduce dose if persistent.

Global Availability and Brands (2026 Update)

Lactulose is available as a generic worldwide and in syrup/powder forms. The global market is growing (estimated ~USD 516-835 million in 2025-2026), driven by rising liver disease and constipation prevalence.

Common brand names (by region)

Duphalac (Abbott) –

Widely available globally.

Constulose, Enulose, Kristalose, Generlac (US/common generics).

Cephulac, Cholac, Chronulac (various).

Europe/Asia: Bifiteral, Laevolac, others.

Emerging: Cadilose (recent launch), generics from Fresenius Kabi, Morinaga, Illovo, Biofac, etc.

Prices vary: ~USD 10-20 for a 500-600 mL bottle in many markets; cheaper generics in developing countries. Over-the-counter in many places for constipation; prescription for HE.

Lactulose remains a cornerstone therapy for constipation and hepatic encephalopathy in 2026 — affordable, effective, and backed by decades of evidence and current guidelines (EASL, AASLD, NHS). It reduces ammonia, prevents HE recurrence, and improves quality of life when used correctly. Always consult a healthcare professional for personalized dosing, especially with liver issues.

For more health tips, pharma insights, or career advice in the pharmaceutical field, follow trusted sources and stay informed. Questions about lactulose brands in your country or related treatments? 

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