Comparative Pharmacology
Head-to-head clinical analysis: CONSTILAC versus MIRALAX.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CONSTILAC versus MIRALAX.
CONSTILAC vs MIRALAX
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.
Polyethylene glycol 3350 (PEG 3350) is an osmotic laxative that works by retaining water in the stool through hydrogen bonding, increasing fecal water content and promoting bowel movements.
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.
17 g (1 heaping tablespoon) dissolved in 4–8 oz of water, juice, soda, coffee, or tea, administered orally once daily. Maximum duration of use: 7 days.
None Documented
None Documented
Not applicable due to negligible systemic absorption; lactulose acts locally in the colon.
Not applicable; polyethylene glycol 3350 is minimally absorbed and systemic half-life is not clinically relevant.
Primarily fecal as unchanged drug (systemic absorption negligible). Renal excretion accounts for <2% of any absorbed fraction. Biliary excretion is minimal.
Primarily excreted unchanged in feces (>90% of oral dose); negligible renal elimination (<0.1% recovered in urine).
Category C
Category C
Osmotic Laxative
Osmotic Laxative