CHRONULAC
Clinical safety rating
cautionComprehensive clinical and safety monograph for CHRONULAC (CHRONULAC).
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 pH, which traps ammonia (NH3) as ammonium (NH4+), reducing serum ammonia levels.
| Metabolism | Not absorbed systemically; metabolized by colonic bacteria (e.g., Lactobacillus, Bacteroides) to lactic acid, acetic acid, and other short-chain fatty acids. |
| Excretion | 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. |
| Half-life | 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. |
| Protein binding | Negligible (<5%), primarily to albumin. |
| Volume of Distribution | Approximately 0.25 L/kg; distributes mainly into extracellular fluid. |
| Bioavailability | Oral: poorly absorbed; <3% reaches systemic circulation as intact lactulose; the remainder is metabolized by colonic bacteria. |
| Onset of Action | Oral: 2-4 hours for laxative effect (lactulose); intravenous: immediate for ammonia reduction (lactulose is not administered IV; CHRONULAC is oral only). Note: CHRONULAC is lactulose, so oral onset for laxative effect is 6-12 hours. |
| Duration of Action | Oral laxative effect: 24-48 hours after a single dose; for hepatic encephalopathy, continuous effect requires regular dosing. |
| Molecular Weight | 342.3 |
10-30 mL orally once daily to twice daily; for acute constipation, 20-30 mL initially; for hepatic encephalopathy, 30-60 mL every 1-2 hours to achieve 2-3 soft stools daily.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment; caution in severe renal impairment due to electrolyte disturbances. |
| Liver impairment | No adjustment needed; used in hepatic encephalopathy at higher doses. |
| Pediatric use | Infants: 2.5-5 mL orally once daily; Children 1-5 years: 5-10 mL once daily; Children 6-12 years: 10-15 mL once daily; Adolescents: 15-30 mL once daily; adjust based on response. |
| Geriatric use | Start at low end of dosing range (10-15 mL once daily) due to increased risk of electrolyte imbalance and dehydration; monitor fluid/electrolyte status. |
| 1st trimester | Limited human data; no known teratogenicity. Use only if clearly needed. |
| 2nd trimester | Generally considered safe; minimal systemic absorption. |
| 3rd trimester | Generally considered safe; minimal systemic absorption. |
Clinical note
Comprehensive clinical and safety monograph for CHRONULAC (CHRONULAC).
| Placental transfer | Not expected to cross placenta due to minimal systemic absorption; molecular weight > 300 Da and water-soluble. |
| Breastfeeding | Lactulose is poorly absorbed orally, and levels in breast milk are expected to be low. Compatible with breastfeeding. |
| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | 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. |
| Fetal Monitoring | No specific maternal or fetal monitoring required beyond routine obstetric care. Monitor for potential electrolyte disturbances (e.g., hypernatremia) if used chronically in high doses, especially in patients with renal impairment. |
| Fertility Effects | No known effects on fertility. Lactulose is not systemically absorbed and has no hormonal or gonadotropic activity. |
■ FDA Black Box Warning
None.
| Serious Effects |
GalactosemiaLactose intoleranceGalactose malabsorptionIntestinal obstructionChronic inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis)
| Precautions | 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) |
| Food/Dietary | No specific food interactions, but avoid concurrent use with other laxatives. Ensure adequate fluid intake to reduce risk of hypernatremia. |
| Clinical Pearls | 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. |
| Patient Advice | 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). |
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