Comparative Pharmacology
Head-to-head clinical analysis: CEPHULAC versus HALFLYTELY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CEPHULAC versus HALFLYTELY.
CEPHULAC vs HALFLYTELY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
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.
PEG 3350 is an osmotic agent that causes water retention in the colon, leading to bowel evacuation. Electrolytes (sodium sulfate, potassium chloride, magnesium sulfate, sodium bicarbonate) prevent significant electrolyte shifts.
30-45 mL (6.67-10 g lactulose) orally 3-4 times daily for constipation; for hepatic encephalopathy, 30-45 mL orally 3-4 times daily titrated to produce 2-3 soft stools per day, or 300 mL in 700 mL of water or saline as retention enema for 30-60 min every 4-6 hours.
Oral: 1 liter (provided as powder for reconstitution) administered at a rate of 240 mL every 10 minutes until rectal effluent is clear or 4 liters total is consumed. Typically given as split-dose: half the volume the evening before and half the morning of colonoscopy.
None Documented
None Documented
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 applicable; PEG 3350 is not significantly absorbed and does not have a systemic half-life. The colon transit time is approximately 1 hour after ingestion.
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).
Primarily fecal elimination of unabsorbed PEG 3350; negligible systemic absorption <0.06%. Electrolytes are excreted renally and fecally.
Category C
Category C
Laxative
Laxative