Classifications: hyperosmotic laxative; Therapeutic: laxative, hyperosmotic
Pregnancy Category: B
10 g/15 mL solution, syrup
Reduces blood ammonia; appears to involve metabolism of lactose to organic acids by resident intestinal bacteria. Acidifies
colon contents, which retards diffusion of nonionic ammonia (NH3) from colon to blood while promoting its migration from blood to colon. In the acidic colon, NH3 is converted to nonabsorbable ammonium ions (NH4+) and is then expelled in feces by laxative action.
Osmotic effect of organic acids causes laxative action, which moves water from plasma to intestines, softening stools, and
stimulates peristalsis by pressure from water content of stool. Decreased blood ammonia in a patient with hepatic encephalopathy
is marked by improved EEG patterns and mental state (clearing of confusion, apathy, and irritation).
Prevention and treatment of portal-systemic encephalopathy (PSE), including stages of hepatic precoma and coma, and by prescription
for relief of chronic constipation.
to restore regular bowel habit posthemorrhoidectomy; to evacuate bowel in older adult patients with severe constipation
after barium studies; and for treatment of chronic constipation in children.
Low galactose diet.
Diabetes mellitus; concomitant use with electrocautery procedures (proctoscopy, colonoscopy); older adult and debilitated
patients; pediatric use; pregnancy (category C); lactation.
Route & Dosage
|Prevention and Treatment of Portal-Systemic Encephalopathy
Adult: PO 3045 mL t.i.d. or q.i.d. adjusted to produce 23 soft stools/d
Adolescent/Child: PO 4090 mL/d in divided doses adjusted to produce 23 soft stools/d
Infant: PO 2.510 mL/d in 34 divided doses adjusted to produce 23 soft stools/d
Management of Acute Portal-Systemic Encephalopathy
Adult: PO 3045 mL q12 h until laxation is achieved, then adjusted to produce 23 soft stools/d. Rectal 300 mL diluted with 700 mL water given via rectal balloon catheter, and retained for 3060 min, may repeat in 46
h if necessary or until patient can take PO
Adult: PO 3060 mL/d prn
Child: PO 7.5 mL/d after breakfast
- Give with fruit juice, water, or milk (if not contraindicated) to increase palatability. Laxative effect is enhanced by taking
with ample liquids. Avoid meal times.
- Administer as a retention enema via a rectal balloon catheter. If solution is evacuated too soon, instillation may be promptly
- Do not freeze. Avoid prolonged exposure to temperatures above 30° C (86° F) or to direct light. Normal darkening
does not affect action, but discard solution that is very dark or cloudy.
Adverse Effects (≥1%)GI:
Flatulence, borborygmi, belching, abdominal cramps, pain, and distention (initial dose); diarrhea
(excessive dose); nausea, vomiting, colon accumulation of hydrogen gas; hypernatremia.
Interactions Drug: laxatives
may incorrectly suggest therapeutic action of lactulose.
Poorly absorbed from GI tract. Metabolism:
In gut by intestinal bacteria.
Assessment & Drug Effects
- In children if the initial dose causes diarrhea, dosage is reduced immediately. Discontinue if diarrhea persists.
- Promote fluid intake (≥15002000 mL/d) during drug therapy for constipation;
older adults often self-limit liquids. Lactulose-induced osmotic changes in the bowel support intestinal water loss and
potential hypernatremia. Discuss strategy with physician.
Patient & Family Education
- Laxative action is not instituted until drug reaches the colon; therefore, about 2448 h is needed.
- Do not self-medicate with another laxative due to slow onset of drug action.
- Notify physician if diarrhea (i.e., more than 2 or 3 soft stools/d) persists more than 2448 h. Diarrhea is a sign
of overdosage. Dose adjustment may be indicated.