lactulose
Brand names: Enulose, Kristalose
Lactulose is a medicine that helps treat and prevent problems with your brain caused by liver disease. It works by reducing the amount of ammonia in your blood.
Drug Pricing (NADAC)
Generic Price
$0.01/unit
Generic Available
Yes (13 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine treats and prevents portal-systemic encephalopathy.
Common side effects
Gas, Bloating, Belching
Key warnings
If you need a low-galactose diet, you should not take this medicine.
How It Works
Lactulose is a sugar that is not digested in your body. It travels to your colon where it is broken down by bacteria. This process makes the colon more acidic, which helps to draw ammonia from the blood into the colon, where it is then removed from the body through bowel movements.
How to Take It
Take lactulose by mouth as directed by your doctor. The usual adult dose is 2 to 3 tablespoonfuls (30 to 45 ml) three or four times a day. You can adjust the dose every day or two to have 2 or 3 soft bowel movements daily. For a quick effect, you may take 30 to 45 ml every hour.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or breastfeeding before taking this medicine. It is not known if lactulose can harm your unborn baby. It is also not known if lactulose passes into breast milk.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is close to your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store lactulose solution between 36° to 86°F (2° to 30°C), and do not freeze it.
Side Effects (from patient reports)
Based on 20,474 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 37,033 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 1997–2025.
Total Reports
37,033
Death-Related Reports
6,511
Hospitalization Reports
20,384
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | NAUSEA | 2,524 |
| 2 | CONSTIPATION | 2,497 |
| 3 | FALL | 2,241 |
| 4 | VOMITING | 2,047 |
| 5 | FATIGUE | 2,027 |
| 6 | DEATH | 1,939 |
| 7 | DYSPNOEA | 1,910 |
| 8 | DIARRHOEA | 1,892 |
| 9 | PAIN | 1,711 |
| 10 | PNEUMONIA | 1,687 |
| 11 | HYPOTENSION | 1,536 |
| 12 | OFF LABEL USE | 1,533 |
| 13 | CONFUSIONAL STATE | 1,482 |
| 14 | PYREXIA | 1,394 |
| 15 | ASTHENIA | 1,326 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
If you need a low-galactose diet, you should not take this medicine. Lactulose solution contains galactose.
Common Questions
Can I take lactulose with other medicines?
How long does it take for lactulose to work?
What should I do if I get diarrhea?
Can children take lactulose?
Does the color change of the medicine mean it has gone bad?
What do I do if the medicine freezes?
Can I mix lactulose with other liquids?
How will I know if the lactulose is working?
What if I still don't have a bowel movement?
Can I take lactulose if I am diabetic?
What are the common side effects of lactulose?
What drug class is lactulose?
Is lactulose safe during pregnancy?
Related Medications in Osmotic Laxative
Other drugs grouped near lactulose — same-class peers and common alternatives.
alosetron
Lotronex
Alosetron (Lotronex) is a medicine for women with severe diarrhea-predominant irritable bowel syndrome (IBS).
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aprepitant
Emend
Aprepitant (Emend) is a medicine that helps prevent nausea and vomiting.
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bisacodyl
Dulcolax
Bisacodyl is a medicine that helps you have a bowel movement.
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bismuth subsalicylate
Pepto-Bismol
Bismuth subsalicylate (Pepto-Bismol) is a medicine that can treat diarrhea and upset stomach.
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cimetidine
Tagamet
Cimetidine (Tagamet) reduces stomach acid.
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What the FDA Data Shows for lactulose
The FDA label for lactulose (sold under brand names such as Enulose, Kristalose) classifies it as a prescription-only medication in the Osmotic Laxative class. This medicine treats and prevents portal-systemic encephalopathy. Official labeling lists 5 commonly reported side effects, including Gas, Bloating, Belching.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 20,474 voluntary reports. Interaction data is drawn directly from FDA-approved prescribing information. NADAC pricing from CMS shows a generic unit cost of $0.01.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: June 1, 2022
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages