Constulose is lactulose. It was one of several brand names for the generic drug lactulose, a synthetic sugar used to treat constipation and liver-related brain dysfunction. Other brand names for the same medication include Cholac, Constilac, Enulose, Generlac, and Kristalose. The Constulose brand has been discontinued in the U.S., but generic lactulose remains widely available.
Why So Many Brand Names Exist
Lactulose is a generic drug, meaning multiple manufacturers can produce and sell it under different brand names. Every version contains the same active ingredient: lactulose, a synthetic disaccharide (a type of sugar molecule). Whether the label says Constulose, Generlac, or simply “lactulose solution,” the medication works identically in your body. The concentration is standardized at 10 grams per 15 mL across formulations.
If you previously took Constulose and your pharmacy now dispenses generic lactulose or a different brand, the switch requires no dosage adjustment. You’re getting the same drug.
How Lactulose Works
Lactulose is a sugar your small intestine can’t break down or absorb. It passes intact into your colon, where gut bacteria ferment it into smaller molecules. These molecules pull water into the bowel through osmosis, softening stool and triggering a bowel movement. The fermentation process also produces gas, which is why bloating and flatulence are common side effects.
For people with liver disease, lactulose serves a different purpose. When the liver can’t properly filter toxins, ammonia builds up in the blood and affects brain function, a condition called hepatic encephalopathy. Lactulose helps by acidifying the colon, which converts ammonia into a form that can’t cross back into the bloodstream. It also speeds up transit through the gut, physically clearing ammonia-producing bacteria. Lactulose is considered the first-line treatment for this condition.
Typical Dosing for Constipation
For chronic constipation, the usual adult dose is 1 to 2 tablespoons (15 to 30 mL) daily, which delivers 10 to 20 grams of lactulose. If that’s not enough, the dose can be increased to 60 mL per day. It typically takes 24 to 48 hours to produce a bowel movement, so it’s not a fast-acting option.
Lactulose also comes as a powder (sold under the brand Kristalose) that you dissolve in water. The powder version avoids the thick, syrupy texture some people find unpleasant.
Making It Easier to Take
Lactulose solution is very sweet, and not everyone finds the taste tolerable. Mixing your dose with half a glass of water or fruit juice can help. You can take it with or without food. One important detail: drink 6 to 8 glasses of water or other fluids throughout the day while using lactulose. Without adequate hydration, the osmotic effect won’t work as well and constipation can actually worsen.
Use the measuring cup or spoon that comes with the bottle rather than a kitchen spoon, which won’t give you an accurate dose.
Side Effects
The most common side effects are gas, bloating, and abdominal cramping. These happen because bacteria in your colon ferment the lactulose, producing hydrogen and carbon dioxide. The gassiness tends to be worst in the first few days and often improves as your body adjusts.
Taking too much lactulose or not drinking enough water can lead to diarrhea, nausea, or electrolyte imbalances. If you’re having more than two to three loose stools per day (outside of hepatic encephalopathy treatment, where the target is higher), the dose is likely too high.
Who Should Avoid Lactulose
Lactulose is not safe for people with galactosemia, a rare inherited condition where the body can’t process the sugar galactose. Since lactulose breaks down into galactose in the colon, it can cause serious problems for these individuals.
If you have diabetes, be aware that high doses of lactulose taken long-term can affect blood sugar levels. People with irritable bowel syndrome should also use caution, since the gas and bloating lactulose produces can worsen IBS symptoms. An alternative laxative may be a better fit in those cases.