Comparative Pharmacology
Head-to-head clinical analysis: CONSTILAC versus PEG LYTE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CONSTILAC versus PEG LYTE.
CONSTILAC vs PEG-LYTE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Constilac (lactulose) is a synthetic disaccharide that is not absorbed in the small intestine. In the colon, it is metabolized by bacteria to short-chain fatty acids (e.g., lactic acid), which osmotically draw water into the bowel, producing a laxative effect. Additionally, in hepatic encephalopathy, the acidification of colonic contents traps ammonia (NH3) as ammonium (NH4+), reducing its absorption.
PEG-LYTE is an osmotic laxative that induces diarrhea by retaining water in the colon through the non-absorbable polyethylene glycol (PEG) and electrolytes, which prevent dehydration and electrolyte imbalance during bowel cleansing.
Oral, 15-45 mL (10-20 g lactulose) once daily, titrated to produce 2-3 soft stools daily; may be given as a single dose or divided twice daily. Onset of action 24-48 hours.
4 liters orally as a single dose or in divided doses for colonoscopy preparation.
None Documented
None Documented
Not applicable due to negligible systemic absorption; lactulose acts locally in the colon.
Not applicable; PEG-3350 is minimally absorbed (<0.06%), thus systemic half-life is not clinically relevant. Local gut transit time ~1-2 hours.
Primarily fecal as unchanged drug (systemic absorption negligible). Renal excretion accounts for <2% of any absorbed fraction. Biliary excretion is minimal.
Primarily fecal (98-99%) as unchanged polyethylene glycol (PEG) 3350; negligible renal excretion (<0.2%). Electrolytes (sodium, potassium, bicarbonate) are partially absorbed and excreted renally.
Category C
Category C
Osmotic Laxative
Osmotic Laxative