Lactulose
ENULOSE
Pronunciation: LAK-tyoo-loes
“Latch loose”
What it isNon-absorbed disaccharide fermented to organic acids; constipation and hepatic encephalopathy.
Why this oneIn encephalopathy it traps ammonia as ammonium in the gut lumen, which no other laxative does.
What limits itBloating and cramping limit adherence. Titrate to two or three soft stools daily; over-treatment causes dehydration and hypernatremia.
Lactulose prescription history
Animated chart of estimated U.S. prescriptions per year, Constipation meds (1900–2026). Lactulose enters in 1977 (estimated).
FDA-approved for
- constipation
- portosystemic encephalopathy
Off-label
- hepatic encephalopathy prophylaxis after a first episode
Principal riskBloating and cramping
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityDiarrhea, dehydration and electrolyte disturbance, especially with excessive or prolonged use.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Constipation | adult | 15-30 mL (10-20 g) QD | 60 mL/day |
Renal Undefined
Hepatic Undefined
Instructions
- 24-48 hours may be required to produce a normal bowel movement
- May mix with fruit juice, water, or milk for acceptability
Available strengths
- sol 10 g/15 mL
Contraindications
- Patients who require a low-galactose diet (contains galactose <1.6 g/15 mL)
Cautions
- Excessive dosage can cause diarrhea with fluid loss, hypokalemia, hypernatremia
Adverse reactions
- Flatulence and intestinal cramps (usually transient)
- Diarrhea with excessive dosage
- Nausea and vomiting
Pregnancy Pregnancy Category B; use during pregnancy only if clearly needed
Lactation Undefined
Cost
| Strength | #/mo | generic $/unit | CostPlus | |
|---|---|---|---|---|
| 10 g/15 mL | sol | per unit | $0.02/mL | offered |
Generic entry1988
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Self-check
- What stool target guides lactulose in hepatic encephalopathy?
Two or three soft stools daily. - How does lactulose trap ammonia in the gut?
Converts it to ammonium.