Sold as Enulose, Constulose, Kristalose, Generlac.
Class: Osmotically acting laxatives.
First FDA approval 03/25/1976: 50 years on the US market.
This grade answers one narrow question: how strong is the public evidence and safety record behind this drug, and how clean is its money trail and court record? It is not a verdict on whether the drug is right for you.
B
Score breakdown (85/100)
Safety ×35%
A
Evidence ×25%
D
Regulatory ×15%
A
Money & lawsuits ×15%
B
Options ×10%
A
Safety: 96
2,690 FDA reports naming it as the suspect drug per million Medicare fills, 1.0x the median drug on this site
Death appears in 1.8x the share of reports seen across all of FAERS (-4)
Evidence: 54
169 randomized trials and 21 systematic reviews/meta-analyses indexed in PubMed
On the WHO Model List of Essential Medicines (shown for context; no score effect)
3 independent Cochrane review(s) exist
Only 22% of completed registered trials posted results (-15)
Regulatory history: 100
No recalls on record since 2016
Money & lawsuits: 85
Pharma paid doctors $156,906 tied to this drug last year (-15)
Not named in any pending federal MDL
Options: 100
Generic versions approved (29 applications)
13 same-class alternatives exist
Independent reviews and post-approval warnings
WHO Essential Medicine
Listed on the WHO Model List of Essential Medicines: a global expert panel judged it among the medicines a health system should always have, on evidence of value, not marketing.
What the FDA label says
Approved uses
INDICATIONS AND USAGE For the treatment of constipation. In patients with a history of chronic constipation, lactulose solution therapy increases the number of bowel movements per day and the number of days on which bowel movements occur.
Contraindications
CONTRAINDICATIONS Since lactulose solution contains galactose (less than 1.6 g/15 mL), it is contraindicated in patients who require a low galactose diet.
Warnings and precautions
WARNINGS A theoretical hazard may exist for patients being treated with lactulose solution who may be required to undergo electrocautery procedures during proctoscopy or colonoscopy. Accumulation of H2 gas in significant concentration in the presence of an electrical spark may result in an explosive reaction. Although this complication has not been reported with lactulose, patients on lactulose therapy undergoing such procedures should have a thorough bowel cleansing with a non-fermentable solution. Insufflation of CO 2 as an additional safeguard may be pursued but is considered to be a redundant measure.
Adverse reactions (label)
ADVERSE REACTIONS 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 REACTIONS, contact Sun Pharmaceutical Industries, Inc. at 1-866-923-4914 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Source: FDA SPL label for Lactulose (Sun Pharmaceutical Industries, Inc.), effective 20250804.
Full label on DailyMed.
Side-effect reports sent to the FDA
These are counts of reports people filed, not rates of harm. Anyone can file one, and nobody checks whether the drug was the cause. Millions of doses are taken for every report sent, so the useful part is how this drug compares with the average across all drugs.
34,118reports that mention this drug
33,942of those blame this drug, not another one the person was taking
88%of reports describe a serious outcome, such as a hospital stay (average for all drugs: 57%)
16.5%of reports include a death, from any cause (average for all drugs: 9.1%)
2,690 reports blaming this drug for every million Medicare prescriptions filled, which is 1.0× the typical drug on this site. (5,431 reports in 2024–2026, against 2,019,249 Medicare fills in one year. This is the one number here that accounts for how many people take the drug.)
Source: the FDA's Adverse Event Reporting System (FAERS). Reports are voluntary and unverified. Drugs that are prescribed a lot, in the news, or in lawsuits attract more reports, so the percentages are compared with the whole database to correct for that partly, not fully.
Counts measure how much evidence exists and how transparent it is, not how big the benefit is. For that, ask your prescriber: if 100 people like me took this, how many would get better because of it, and how many would be harmed? (Doctors call these the "number needed to treat" and "number needed to harm.") It differs by condition and is the number drug ads leave out. Sources: PubMed, ClinicalTrials.gov.
Money and lawsuits
In 2024, drug companies reported $156,906 in payments to US physicians and hospitals tied to this drug across 1,189 transactions (Kristalose $156,906).
No pending federal MDL names this drug or its brands.
Not named in any federal pharmaceutical settlement of $100M or more on record.
Sources: CMS Open Payments (Sunshine Act); Judicial Panel on Multidistrict Litigation pending docket list; DOJ settlements as tabulated on Wikipedia with links to the primary record. State-court and individual suits are not included.
Same ATC pharmacological class, graded ones first, best grade at the top. Being in the same class does not make them interchangeable for your condition; it makes them worth asking about.
Questions to ask your prescriber
The most-reported problems in FDA's adverse event data are constipation, nausea, fall, fatigue. How would we recognize and handle those?
Why this one over lactitol, magnesium carbonate, magnesium citrate? What would make you pick one of those instead?
What result are we expecting, by when, and what is the plan if it does not happen?
If 100 people like me took this drug, how many would actually get better because of it, and how many would be harmed by it? (Doctors call these the number needed to treat and the number needed to harm.)