Lactulose
Lactulose
Generic Name
Lactulose
Mechanism
- Unabsorbable disaccharide that draws water into the colon via osmosis → softens stool and accelerates transit.
- Fermentation by colonic bacteria → short‑chain fatty acids (acetate, propionate, butyrate) that lower colonic pH.
- Lowered pH converts ammonium (NH₃) to non‑absorbable ammonium (NH₄⁺), reducing serum ammonia and cerebral toxicity in hepatic encephalopathy.
Pharmacokinetics
| Parameter | Details |
| Absorption | Minimal; <1 % absorbed in the small intestine. |
| Distribution | Primarily confined to the gastrointestinal tract. |
| Metabolism | Bacterial fermentation in colon to SCFAs. |
| Elimination | Unchanged lactulose excreted in feces; SCFAs absorbed by colonic mucosa. |
| Half‑life | Not applicable; dependent on GI motility and stool consistency. |
Indications
- Chronic constipation in adults and children (≥12 yrs).
- Acute or chronic hepatic encephalopathy (decompensated cirrhosis, portosystemic shunt).
- Hyperammonemia from liver failure, metabolic disorders, or nitrogen load.
Contraindications
- Contraindications
- Severe renal insufficiency (may impair fluid delivery).
- Dehydration; ensure adequate fluid intake.
- Warnings
- Use cautiously in patients with diarrheal disease (risk of severe osmotic diarrhea).
- Avoid during pregnancy if unnecessary; lactulose is Category B but not essential.
- Monitor for electrolyte disturbances (hypokalemia, hyponatremia) in patients on diuretics.
Dosing
| Condition | Dose | Titration | Administration route |
| Constipation (adult) | 10–30 g (1–3 Tbsp) daily, starting low | Increase by 5 g (1 Tbsp) every 2–3 days to achieve 2–3 soft stool/day | Oral (syrup, gel, powder) |
| Hepatic encephalopathy | 10–20 g (2–4 Tbsp) every 6 hrs as needed | Keep stool soft, 2–3 times/day. Titrate for ammonia reduction | Oral (syrup) |
| Pediatric (≥12 yrs) | 0.5–1 mL/kg (0.1–0.2 g/kg) BID | Adjust to stool frequency | Oral |
• Mix with water (1:1) or directly from vial for pediatric or elderly patients.
• Avoid concurrent use with sucralose or other sweeteners that may interfere with stool consistency.
Adverse Effects
Common
• Osmotic diarrhea
• Bloating, flatulence
• Abdominal cramping
• Nausea
Serious
• Electrolyte abnormalities (hypokalemia, hyponatremia)
• Severe dehydration (especially in high‑dose or renal impairment)
• Hypersensitivity reactions (rare)
Monitoring
- Stool frequency & consistency (target 2–3 soft stools/day).
- Serum ammonia in hepatic encephalopathy (baseline, 24 hrs, then Q3–7 days).
- Electrolytes (Na⁺, K⁺, Cl⁻) if fluid status altered or diuretics used.
- Weight & hydration status in at-risk patients.
- Liver function tests during long‑term use.
Clinical Pearls
- Start low, go slow: Begin with 5 g (1 Tbsp) BID; titrate to desired stool frequency.
- Sodium vs. lactitol: Sodium lactulose may be preferable in hyponatremic patients; lactitol adds a potassium load—use cautiously in renal disease.
- Avoid mixing with other osmotic laxatives (e.g., polyethylene glycol) to prevent exaggerated diarrhea.
- Use as a bridge: In hepatic encephalopathy, initiate lactulose while awaiting treatment of precipitating factors (infection, electrolyte disturbance).
- Patient education: Emphasize adequate fluid intake to mitigate dehydration risk.
- Home monitoring: Provide patients with a diary to record stool numbers and consistency—helps titrate dose effectively.
- Alternate formulations: In pediatrics or dysphagia, the powder can be measured with a syringe or diluted in applesauce, improving adherence.
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• Key Takeaway: Lactulose is a time‑honed, safe, and effective agent for both constipation and hepatic encephalopathy, acting via osmotic and microbiologic pathways to lower serum ammonia. Proper titration, monitoring, and patient education are essential to maximize benefit and minimize common GI side effects.