Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES vs CHRONULAC
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Polyethylene glycol 3350 is an osmotic laxative that acts by retaining water in the stool, increasing stool volume, and stimulating colonic peristalsis. Electrolytes (sodium sulfate, potassium sulfate, magnesium sulfate) are included to maintain fluid and electrolyte balance and prevent shifts.
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.
Bowel cleansing prior to colonoscopy,Treatment of acute constipation in specific formulations
Treatment of constipation,Hepatic encephalopathy (portal-systemic encephalopathy)
4 liters of PEG-3350 and electrolytes solution orally as a single dose for colonoscopy preparation; alternative split-dose regimen: 2 liters evening before and 2 liters morning of procedure. For constipation: 17 g (1 heaping tablespoon) dissolved in 8 oz water once daily, up to 3 days.
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.
Not applicable; PEG 3350 is not metabolized and is eliminated non-kinetically. Clinical effect occurs during colonic transit; residual drug cleared within 24–48 hours post-dose.
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.
Polyethylene glycol 3350 is not significantly metabolized; it is excreted unchanged in feces and urine. Electrolytes are absorbed and metabolized according to normal physiological pathways.
Not absorbed systemically; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to lactic acid, acetic acid, and other short-chain fatty acids.
Primarily fecal (unchanged); minimal renal excretion (<2%) as intact polymer. Electrolytes absorbed and renally excreted.
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.
PEG 3350: <1% bound to plasma proteins.
Negligible (<5%), primarily to albumin.
PEG 3350: 0.58 L/kg (confined to extracellular fluid; minimal tissue penetration).
Approximately 0.25 L/kg; distributes mainly into extracellular fluid.
Oral: <0.06% for PEG 3350 (systemic absorption negligible). Electrolytes fully absorbed.
Oral: poorly absorbed; <3% reaches systemic circulation as intact lactulose; the remainder is metabolized by colonic bacteria.
Contraindicated in patients with GFR < 30 m L/min/1.73 m² due to risk of electrolyte abnormalities and fluid overload. For GFR 30-60: use with caution, monitor electrolytes and volume status; consider split-dose regimen.
No dose adjustment required for renal impairment; caution in severe renal impairment due to electrolyte disturbances.
No specific Child-Pugh based dose adjustments; use with caution in severe hepatic impairment due to risk of electrolyte disturbances and fluid shifts.
No adjustment needed; used in hepatic encephalopathy at higher doses.
For colonoscopy: 4 L if ≥ 12 years old; for constipation: 0.5-1.5 g/kg/day (max 17 g/day) in children ≥ 6 months. Safety and efficacy not established for colonoscopy in children < 12 years; alternative polyethylene glycol products available.
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.
Use with caution due to increased risk of electrolyte imbalance, aspiration, and fluid overload. Consider split-dose regimen, monitor renal function and electrolytes. Lower starting dose for constipation: 8.5 g daily.
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.
No FDA black box warning.
None.
Risk of fluid and electrolyte abnormalities,Serious arrhythmias in patients with pre-existing electrolyte disturbances,Seizures,Renal impairment,Aspiration risk in patients with impaired gag reflex,Colonic mucosal ulcerations
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)
Gastrointestinal obstruction,Gastric retention,Bowel perforation,Toxic colitis,Toxic megacolon,Ileus,Known hypersensitivity to any component
Patients with galactosemia,Intestinal obstruction,Known hypersensitivity to lactulose
Avoid solid food during bowel preparation. Clear liquids only: water, clear broth, apple juice, white grape juice, black coffee or tea (no milk), clear sports drinks, gelatin without fruit. No red or purple colored liquids. Avoid alcohol.
No specific food interactions, but avoid concurrent use with other laxatives. Ensure adequate fluid intake to reduce risk of hypernatremia.
Insufficient human data; animal studies not conducted. Use during pregnancy only if clearly needed. No known teratogenicity from limited reports.
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.
Excretion into breast milk unknown; polyethylene glycol is minimally absorbed systemically. Considered likely compatible with breastfeeding due to low absorption.
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.
No dose adjustment required; pharmacokinetic changes in pregnancy are not expected to alter efficacy or safety due to minimal systemic 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).
Administer in divided doses to improve tolerance. Ensure adequate hydration to prevent electrolyte imbalance. Contraindicated in ileus, gastrointestinal obstruction, perforation, gastric retention, or toxic colitis. Use with caution in patients with impaired gag reflex to reduce aspiration risk. Monitor renal function and electrolytes in elderly or debilitated patients.
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.
Take this medication exactly as prescribed for bowel preparation before colonoscopy.,Mix the powder with clear liquids as directed; do not consume any solid food during preparation.,Drink additional clear fluids throughout the preparation to stay hydrated.,Expect frequent, watery bowel movements; stay near a toilet.,If you experience severe abdominal pain, vomiting, or inability to pass stool, contact your doctor immediately.
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).
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 POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES vs CHRONULAC, answered by our medical review team.
POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES is a Bowel Evacuant that works by Polyethylene glycol 3350 is an osmotic laxative that acts by retaining water in the stool, increasing stool volume, and stimulating colonic peristalsis. Electrolytes (sodium sulfate, potassium sulfate, magnesium sulfate) are included to maintain fluid and electrolyte balance and prevent shifts.. 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES and CHRONULAC 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 POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES is: 4 liters of PEG-3350 and electrolytes solution orally as a single dose for colonoscopy preparation; alternative split-dose regimen: 2 liters evening before and 2 liters morning of procedure. For constipation: 17 g (1 heaping tablespoon) dissolved in 8 oz water once daily, up to 3 days.. 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.. 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 POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES and CHRONULAC 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. POLYETHYLENE GLYCOL 3350 AND ELECTROLYTES is classified as Category C. Insufficient human data; animal studies not conducted. Use during pregnancy only if clearly needed. No known teratogenicity from limited reports.. 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 . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.