Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CHRONULAC vs CHOLAC
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Lactulose is a synthetic disaccharide that is not absorbed in the small intestine. It is hydrolyzed by colonic bacteria to form low molecular weight acids (mainly lactic and acetic acid), which osmotically draw water into the colon, softening stools and increasing stool frequency. Additionally, lactulose decreases colonic p H, which traps ammonia (NH3) as ammonium (NH4+), reducing serum ammonia levels.
Lactulose is a synthetic disaccharide that is not absorbed in the small intestine. It is metabolized by colonic bacteria to short-chain fatty acids, primarily lactic acid and acetic acid, which lower the colonic p H. This acidification traps ammonia (NH3) as ammonium (NH4+) in the gut lumen, reducing serum ammonia levels. Additionally, the osmotic effect of lactulose draws water into the colon, producing a laxative effect.
Treatment of constipation,Hepatic encephalopathy (portal-systemic encephalopathy)
Treatment of hepatic encephalopathy (portal-systemic encephalopathy) in patients with acute and chronic liver disease,Constipation (including chronic idiopathic constipation)
10-30 m L orally once daily to twice daily; for acute constipation, 20-30 m L initially; for hepatic encephalopathy, 30-60 m L every 1-2 hours to achieve 2-3 soft stools daily.
15-30 m L (10-20 g lactulose) orally once daily, titrated to produce 2-3 soft stools per day; maximum dose 60 m L/day. For hepatic encephalopathy: 30-45 m L (20-30 g) orally 3-4 times daily, titrated to 2-3 soft stools per day.
Terminal elimination half-life approximately 1.5-2.5 hours in adults with normal renal function; may be prolonged to 4-8 hours in patients with renal impairment.
0.5-1.5 hours for lactulose; active metabolites (e.g., acetic acid) have negligible systemic half-life due to rapid local metabolism.
Not absorbed systemically; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to lactic acid, acetic acid, and other short-chain fatty acids.
Not absorbed systemically. Metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to lactic acid, acetic acid, and other short-chain fatty acids.
Primarily renal (as unchanged drug and metabolites): ~40-50% of dose excreted in urine within 24 hours; biliary/fecal elimination accounts for the remainder, with approximately 2-5% recovered in feces as parent compound.
Primarily fecal (biliary excretion of unchanged drug and metabolites); minimal renal excretion (<5%).
Negligible (<5%), primarily to albumin.
Negligible (<1%); not significantly bound to plasma proteins.
Approximately 0.25 L/kg; distributes mainly into extracellular fluid.
Approximately 0.2 L/kg; indicates distribution primarily in extracellular fluid.
Oral: poorly absorbed; <3% reaches systemic circulation as intact lactulose; the remainder is metabolized by colonic bacteria.
Oral: <2% systemic bioavailability due to extensive first-pass metabolism and local gut action; rectal: minimal systemic absorption.
No dose adjustment required for renal impairment; caution in severe renal impairment due to electrolyte disturbances.
No dose adjustment required for renal impairment.
No adjustment needed; used in hepatic encephalopathy at higher doses.
No specific Child-Pugh based adjustments. Use with caution in severe hepatic impairment due to risk of electrolyte disturbances; monitor serum electrolytes.
Infants: 2.5-5 m L orally once daily; Children 1-5 years: 5-10 m L once daily; Children 6-12 years: 10-15 m L once daily; Adolescents: 15-30 m L once daily; adjust based on response.
Infants: 2.5-10 m L/day in divided doses. Children: 40-90 mg/kg/day (as lactulose) divided 1-2 times daily, titrated to produce soft stools. For hepatic encephalopathy: 2.5-10 m L (1.7-6.7 g) orally 3-4 times daily, titrated to 2-3 soft stools per day.
Start at low end of dosing range (10-15 m L once daily) due to increased risk of electrolyte imbalance and dehydration; monitor fluid/electrolyte status.
Initiate at lower end of dosing range (15 m L once daily) and titrate slowly to avoid diarrhea and electrolyte imbalance; monitor renal function and electrolytes.
None.
No FDA black box warning.
Electrolyte disturbances (e.g., hypernatremia, hypokalemia) with prolonged use or high doses,Diarrhea may cause fluid and electrolyte loss,Risk of colonic distention or fecal impaction,Use caution in patients with galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption (contains galactose and lactose)
Electrolyte disturbances (e.g., hypernatremia) may occur, especially with prolonged use or in patients with renal impairment,Diarrhea can lead to fluid and electrolyte loss; dosage should be adjusted to produce 2-3 soft stools per day,Galactose content: lactulose contains galactose and lactose; use with caution in patients with galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption,Risk of colonic perforation in patients with severe colonic ulceration, toxic megacolon, or gastrointestinal obstruction
Patients with galactosemia,Intestinal obstruction,Known hypersensitivity to lactulose
Patients with galactosemia (due to galactose content),Gastrointestinal obstruction (including ileus),Hypersensitivity to lactulose or any component of the formulation
No specific food interactions, but avoid concurrent use with other laxatives. Ensure adequate fluid intake to reduce risk of hypernatremia.
No specific food restrictions. Mixing with fruit juice, water, or milk may improve taste. Avoid excessive intake of dairy products if lactose intolerant (lactulose may contain small amounts of lactose).
Lactulose (CHRONULAC) is not absorbed systemically; no teratogenic effects are expected. No adequate and well-controlled studies in pregnant women; animal reproduction studies not conducted. Based on lack of systemic absorption, risk to fetus is low across all trimesters.
Lactulose is not absorbed systemically; no teratogenic effects reported in animal studies or human case reports. FDA Pregnancy Category B. Trimester-specific risks: no known fetal harm in any trimester.
Lactulose is not absorbed orally; therefore, excretion into breast milk is negligible. Considered compatible with breastfeeding; no M/P ratio available due to lack of systemic absorption.
Excretion into breast milk is negligible due to minimal systemic absorption. M/P ratio not determined. Considered compatible with breastfeeding.
No dose adjustment required during pregnancy. Pharmacokinetics of lactulose are unchanged due to lack of systemic absorption. Use standard dosing for constipation (15-30 m L daily, titrated to effect).
No dose adjustment required during pregnancy; pharmacokinetics unchanged due to localized GI action.
Chronulac (lactulose) is a non-absorbable disaccharide used for constipation and hepatic encephalopathy. Onset of action for constipation is 24-48 hours; monitor for electrolyte disturbances (hypernatremia) with prolonged use. Do not use with other laxatives in acute abdomen. For hepatic encephalopathy, titrate to 2-3 soft stools daily.
Cholac (lactulose) is used for constipation and hepatic encephalopathy. Monitor for diarrhea and electrolyte imbalances. In hepatic encephalopathy, titrate dose to achieve 2-3 soft stools per day. Syrup can be mixed with fruit juice or water to improve palatability. Onset of action is 24-48 hours for constipation; for encephalopathy, effects may take several days.
May take 24-48 hours to produce a bowel movement; do not use if you have abdominal pain, nausea, or vomiting.,Mix with fruit juice, milk, or water to improve taste.,Store at room temperature; do not freeze.,Report excessive diarrhea or electrolyte imbalance symptoms (muscle cramps, weakness).
Take exactly as prescribed. Do not change dose without consulting your doctor.,For constipation, effects may take up to 48 hours. Do not use other laxatives unless advised.,For liver disease, it helps reduce ammonia levels. Aim for 2-3 soft bowel movements daily.,May cause gas, bloating, or stomach cramps, which usually decrease over time.,Contact doctor if you have severe diarrhea, vomiting, or signs of dehydration.,Store at room temperature, away from heat and direct light.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CHRONULAC vs CHOLAC, answered by our medical review team.
CHRONULAC is a Osmotic Laxative that works by Lactulose is a synthetic disaccharide that is not absorbed in the small intestine. It is hydrolyzed by colonic bacteria to form low molecular weight acids (mainly lactic and acetic acid), which osmotically draw water into the colon, softening stools and increasing stool frequency. Additionally, lactulose decreases colonic p H, which traps ammonia (NH3) as ammonium (NH4+), reducing serum ammonia levels.. CHOLAC is a Laxative that works by Lactulose is a synthetic disaccharide that is not absorbed in the small intestine. It is metabolized by colonic bacteria to short-chain fatty acids, primarily lactic acid and acetic acid, which lower the colonic p H. This acidification traps ammonia (NH3) as ammonium (NH4+) in the gut lumen, reducing serum ammonia levels. Additionally, the osmotic effect of lactulose draws water into the colon, producing a laxative effect.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CHRONULAC and CHOLAC depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CHRONULAC is: 10-30 m L orally once daily to twice daily; for acute constipation, 20-30 m L initially; for hepatic encephalopathy, 30-60 m L every 1-2 hours to achieve 2-3 soft stools daily.. The standard adult dose of CHOLAC is: 15-30 m L (10-20 g lactulose) orally once daily, titrated to produce 2-3 soft stools per day; maximum dose 60 m L/day. For hepatic encephalopathy: 30-45 m L (20-30 g) orally 3-4 times daily, titrated to 2-3 soft stools per day.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between CHRONULAC and CHOLAC in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. CHRONULAC is classified as Category C. Lactulose (CHRONULAC) is not absorbed systemically; no teratogenic effects are expected. No adequate and well-controlled studies in pregnant women; animal reproduction studies not . CHOLAC is classified as Category C. Lactulose is not absorbed systemically; no teratogenic effects reported in animal studies or human case reports. FDA Pregnancy Category B. Trimester-specific risks: no known fetal . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.