Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CHRONULAC vs CEPHULAC
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, a synthetic disaccharide, is not absorbed from the gastrointestinal tract. It is metabolized by colonic bacteria to form short-chain fatty acids (e.g., lactic, acetic, formic acids), which acidify the colonic contents. In hepatic encephalopathy, the acidic environment converts ammonia (NH3) to ammonium (NH4+), which is poorly absorbed and excreted in feces. Additionally, the osmotic effect of lactulose draws water into the colon, softening stools and increasing bowel movements.
Treatment of constipation,Hepatic encephalopathy (portal-systemic encephalopathy)
Treatment of constipation,Hepatic encephalopathy (portal-systemic encephalopathy) including the prevention and treatment of coma
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.
30-45 m L (6.67-10 g lactulose) orally 3-4 times daily for constipation; for hepatic encephalopathy, 30-45 m L orally 3-4 times daily titrated to produce 2-3 soft stools per day, or 300 m L in 700 m L of water or saline as retention enema for 30-60 min every 4-6 hours.
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.
Terminal elimination half-life is 7-10 hours (renal impairment: prolonged); systemic absorption is minimal (<3%) after oral administration, so half-life reflects clearance of absorbed fraction.
Not absorbed systemically; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to lactic acid, acetic acid, and other short-chain fatty acids.
Not absorbed; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to low molecular weight organic 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 renal (20-30% as unchanged drug) and fecal (up to 70% as unmetabolized drug via biliary elimination; following gastric acid-mediated degradation, only 5-10% reaches urine as intact lactulose; hepatic metabolism is negligible).
Negligible (<5%), primarily to albumin.
Negligible (<5%): lactulose does not bind significantly to albumin or other plasma proteins due to its hydrophilic nature.
Approximately 0.25 L/kg; distributes mainly into extracellular fluid.
0.5-1.0 L/kg (estimated from systemic absorption studies; limited data due to minimal absorption; reflects distribution largely into extracellular water).
Oral: poorly absorbed; <3% reaches systemic circulation as intact lactulose; the remainder is metabolized by colonic bacteria.
Oral: <3% (due to poor absorption and extensive metabolism by colonic bacteria; most of the drug remains in the gut lumen). Rectal: similar to oral, as systemic absorption is minimal.
No dose adjustment required for renal impairment; caution in severe renal impairment due to electrolyte disturbances.
No dose adjustment required for renal impairment as lactulose is minimally absorbed and primarily acts locally in the colon.
No adjustment needed; used in hepatic encephalopathy at higher doses.
Not specifically adjusted based on Child-Pugh score; dose is titrated to achieve desired stool frequency; caution in severe hepatic impairment due to risk of electrolyte disturbances.
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; older children: 10-25 m L/day; adolescents: 15-30 m L/day; all for constipation; for hepatic encephalopathy, doses as low as 5-10 m L 3-4 times daily with dose adjusted to produce 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 (15-30 m L/day) due to increased risk of dehydration and electrolyte imbalance; monitor for diarrhea and adjust accordingly.
None.
None
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 imbalance with prolonged use, especially in debilitated patients,Diarrhea may cause fluid and electrolyte loss,Galactose intolerance (contraindicated in patients requiring low galactose diet due to lactose content in some preparations),Monitor serum electrolytes in patients receiving high doses for hepatic encephalopathy
Patients with galactosemia,Intestinal obstruction,Known hypersensitivity to lactulose
Patients requiring a low-galactose diet (lactulose contains galactose and lactose),Intestinal obstruction,Suspected gastrointestinal obstruction or perforation
No specific food interactions, but avoid concurrent use with other laxatives. Ensure adequate fluid intake to reduce risk of hypernatremia.
No specific food interactions. Avoid concurrent use with other laxatives unless directed. High-fiber foods may enhance effect; ensure adequate fluid intake.
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 (CEPHULAC) is not absorbed systemically; therefore, fetal exposure is negligible. Animal studies have not shown teratogenic effects. In clinical practice, no fetal risks have been identified 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.
Lactulose is not excreted into breast milk due to minimal systemic absorption. It is considered compatible with breastfeeding. M/P ratio: Not applicable (negligible absorption).
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. Pharmacokinetics are unchanged in pregnancy due to lack of systemic absorption. Standard dosing of 15-30 m L (10-20 g) once daily, up to 60 m L/day in divided doses, is appropriate.
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.
Cephulac (lactulose) is a non-absorbable disaccharide used for constipation and hepatic encephalopathy. In hepatic encephalopathy, titrate to produce 2-3 soft stools per day. Monitor serum electrolytes, especially in elderly or renal impairment. Onset of action for constipation may be 24-48 hours. Do not confuse with other lactose-containing products.
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; may take 24-48 hours to produce a bowel movement.,For hepatic encephalopathy, maintain 2-3 soft stools daily; do not skip doses.,May cause bloating, gas, or cramping initially; usually resolves.,Do not take other laxatives without consulting your doctor.,Report severe diarrhea, vomiting, or muscle cramps to your healthcare provider.
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 CEPHULAC, 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.. CEPHULAC is a Laxative that works by Lactulose, a synthetic disaccharide, is not absorbed from the gastrointestinal tract. It is metabolized by colonic bacteria to form short-chain fatty acids (e.g., lactic, acetic, formic acids), which acidify the colonic contents. In hepatic encephalopathy, the acidic environment converts ammonia (NH3) to ammonium (NH4+), which is poorly absorbed and excreted in feces. Additionally, the osmotic effect of lactulose draws water into the colon, softening stools and increasing bowel movements.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CHRONULAC and CEPHULAC 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 CEPHULAC is: 30-45 m L (6.67-10 g lactulose) orally 3-4 times daily for constipation; for hepatic encephalopathy, 30-45 m L orally 3-4 times daily titrated to produce 2-3 soft stools per day, or 300 m L in 700 m L of water or saline as retention enema for 30-60 min every 4-6 hours.. 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 CEPHULAC 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 . CEPHULAC is classified as Category C. Lactulose (CEPHULAC) is not absorbed systemically; therefore, fetal exposure is negligible. Animal studies have not shown teratogenic effects. In clinical practice, no fetal risks . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.