Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
COLOVAGE vs CEPHULAC
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
COLOVAGE is a bowel cleansing preparation containing polyethylene glycol 3350 and electrolytes. It acts as an osmotic laxative, causing fluid retention in the colon to stimulate bowel evacuation.
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.
Colonoscopy preparation,Bowel cleansing prior to colorectal surgery
Treatment of constipation,Hepatic encephalopathy (portal-systemic encephalopathy) including the prevention and treatment of coma
4 liters of PEG-3350 electrolyte solution orally as a single dose for colon cleansing prior to colonoscopy; alternatively, 2 liters with ascorbic acid regimen.
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.
Not applicable (non-absorbed, gut lavage); systemic absorption minimal
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.
Polyethylene glycol 3350 is not absorbed systemically; no hepatic metabolism.
Not absorbed; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to low molecular weight organic acids.
Primarily fecal as unabsorbed drug; negligible renal excretion (<5%)
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).
Not applicable (minimal systemic absorption)
Negligible (<5%): lactulose does not bind significantly to albumin or other plasma proteins due to its hydrophilic nature.
Not applicable (limited to gastrointestinal tract)
0.5-1.0 L/kg (estimated from systemic absorption studies; limited data due to minimal absorption; reflects distribution largely into extracellular water).
Oral: <0.3% systemically absorbed
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.
Contraindicated in GFR <30 m L/min/1.73 m²; for GFR 30-60 m L/min/1.73 m², use with caution due to risk of electrolyte imbalance, no dose adjustment recommended.
No dose adjustment required for renal impairment as lactulose is minimally absorbed and primarily acts locally in the colon.
No specific Child-Pugh based adjustments; use with caution in severe hepatic impairment due to potential fluid and electrolyte disturbances.
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.
Not indicated for patients under 18 years of age; no established weight-based dosing.
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.
No specific dose adjustment, but monitor for electrolyte disturbances, dehydration, and aspiration risk; consider split-dose regimen or lower volume if tolerated.
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.
Risk of fluid and electrolyte abnormalities (e.g., hyponatremia, seizures) in patients with impaired renal function, dehydration, or those taking medications affecting electrolytes.
None
Monitor for fluid and electrolyte disturbances, especially in elderly, debilitated, or renal impaired patients. Use with caution in patients with gastrointestinal obstruction, ileus, or severe colitis.
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
Gastrointestinal obstruction, ileus, gastric retention, bowel perforation, toxic colitis or megacolon, hypersensitivity to any component.
Patients requiring a low-galactose diet (lactulose contains galactose and lactose),Intestinal obstruction,Suspected gastrointestinal obstruction or perforation
Only clear liquids (e.g., water, clear broth, black coffee/tea, clear juices) are allowed during bowel preparation. Avoid all solid foods, dairy products, red or purple liquids, and alcohol. Do not consume any food containing pulp or seeds.
No specific food interactions. Avoid concurrent use with other laxatives unless directed. High-fiber foods may enhance effect; ensure adequate fluid intake.
Colovage (polyethylene glycol 3350) is not absorbed systemically; no teratogenic risk anticipated in any trimester. No fetal risks reported with oral use.
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.
Due to lack of systemic absorption, excretion into breast milk is negligible. Colovage is considered compatible with breastfeeding. M/P ratio: not applicable.
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 necessary; pharmacokinetics unchanged as drug is not absorbed.
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.
COLOVAGE (polyethylene glycol 3350, sodium sulfate, sodium chloride, potassium chloride, sodium ascorbate, ascorbic acid) is a high-volume colon cleansing preparation. Ensure adequate hydration before, during, and after use. Monitor for electrolyte disturbances in patients with renal impairment or those taking diuretics. Split-dose regimen improves tolerance and cleansing quality. Avoid use in patients with gastrointestinal obstruction, perforation, or toxic megacolon.
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.
Follow the split-dose regimen exactly as prescribed to achieve optimal bowel cleansing.,Drink additional clear liquids as directed to prevent dehydration.,Do not eat any solid food while taking the preparation; only clear liquids are allowed.,Expect frequent, watery stools; stay near a restroom.,Contact your doctor if you experience severe abdominal pain, vomiting, or signs of dehydration.
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 COLOVAGE vs CEPHULAC, answered by our medical review team.
COLOVAGE is a Osmotic Laxative that works by COLOVAGE is a bowel cleansing preparation containing polyethylene glycol 3350 and electrolytes. It acts as an osmotic laxative, causing fluid retention in the colon to stimulate bowel evacuation.. 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 COLOVAGE 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 COLOVAGE is: 4 liters of PEG-3350 electrolyte solution orally as a single dose for colon cleansing prior to colonoscopy; alternatively, 2 liters with ascorbic acid regimen.. 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 COLOVAGE 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. COLOVAGE is classified as Category C. Colovage (polyethylene glycol 3350) is not absorbed systemically; no teratogenic risk anticipated in any trimester. No fetal risks reported with oral use.. 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.