Lactulose: uses, dosing, side effects & brands
Lactulose is an osmotic laxative sold in the U.S. under 3 brand and generic names, for constipation and hepatic encephalopathy. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Osmotic Laxative
- Treats (across its forms)
- Constipation and Hepatic Encephalopathy
- Available as
- Solution · Powder
- Sold as
- 3 products — Cephulac, Chronulac and Lactulose
- Prescription?
- Prescription only
- Generic available?
- Yes
- What the pharmacy pays
- about $0.72 for a 30-count supply — not your price
How lactulose is dosed
From the FDA label for Lactulose (application ANDA090503). Other lactulose products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
The usual dose is 1 to 2 tablespoonfuls (15 to 30 mL, containing 10 g to 20 g of lactulose) daily. The dose may be increased to 60 mL daily if necessary. Twenty-four to 48 hours may be required to produce a normal bowel movement. Note: Some patients have found that lactulose solution may be more acceptable when mixed with fruit juice, water or milk.
Lactulose side effects
Precise frequency data are not available. Initial dosing may produce flatulence and intestinal cramps, which are usually transient. Excessive dosage can lead to diarrhea with potential complications such as loss of fluids, hypokalemia, and hypernatremia. Nausea and vomiting have been reported. To report SUSPECTED ADVERSE EVENTS, contact the FDA at 1-800-FDA-1088 or http://www.fda.gov/ for voluntary reporting of adverse reactions.
Who shouldn’t take lactulose
Since lactulose solution contains galactose (less than 1.6 g/15 mL), it is contraindicated in patients who require a low galactose diet.
Lactulose drug interactions
Results of preliminary studies in humans and rats suggest that non-absorbable antacids given concurrently with lactulose may inhibit the desired lactulose-induced drop in colonic pH. Therefore, a possible lack of desired effect of treatment should be taken into consideration before such drugs are given concomitantly with lactulose solution.
Every lactulose product we track (3)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 70/100 | Prescription | Solution | Generic | $1 | View → | |
| 2 | 70/100 | Prescription | Solution | Generic | $1 | View → | |
| 3 | 68/100 | Prescription | Solution | Generic | $1 | View → |
How long lactulose keeps
No lactulose label we read sets a separate limit for after opening, but they do specify how it must be stored — and the stability behind any date assumes those conditions.
Does lactulose expire? The in-use limits and storage rules from its labelsWhat people report to the FDA about lactulose
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 38,215 reports naming lactulose, and the FDA flagged 89% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- nausea2,584 reports
- constipation2,541 reports
- fall2,281 reports
- vomiting2,141 reports
- fatigue2,034 reports
- diarrhoea1,961 reports
- dyspnoea1,950 reports
- pneumonia1,724 reports
Read these as a signal, not a rate. A report does not mean lactulose caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
What is lactulose?
Lactulose is an osmotic laxative used to treat Constipation, Hepatic Encephalopathy.
What kind of drug is lactulose?
The FDA classifies lactulose as an osmotic laxative. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take lactulose with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run lactulose against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is lactulose sold under?
We track 3 lactulose-containing products in the U.S.: Cephulac, Chronulac and Lactulose. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does lactulose come in?
Across the brands we track, lactulose is currently marketed as solution and powder, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic lactulose?
Yes. Our catalog lists 1 generic lactulose product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Lactulose: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/lactulose
- MLA
- “Lactulose: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/lactulose.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for lactulose on DailyMed (NIH) ↗.