Avolac Concentrated Oral Solution

Avolac causes a decrease in blood ammonia concentration and reduces the degree of portal-systemic encephalopathy. These actions are considered to be results of the following:

  • Bacterial degradation of lactulose in the colon acidifies the colonic contents.
  • This acidification of colonic contents results in the retention of ammonia in the colon as the ammonium ion. Since the colonic contents are then more acid than the blood, ammonia can be expected to migrate from the blood into the colon to form the ammonium ion.
  • The acid colonic contents convert NH3 to the ammonium ion (NH4)+, trapping it and preventing its absorption.
  • The laxative action of the metabolites of lactulose then expels the trapped ammonium ion from the colon.
  • Experimental data indicate that lactulose is poorly absorbed. Avolac given orally to man and experimental animals resulted in only small amounts reaching the blood. Urinary excretion has been determined to be 3% or less and is essentially complete within 24 hours.
  • When incubated with extracts of human small intestinal mucosa, lactulose was not hydrolyzed during a 24-hour period and did not inhibit the activity of these extracts on lactose. Avolac reaches the colon essentially unchanged. There it is metabolized by bacteria with the formation of low molecular weight acids that acidify the colon contents.


Avolac is used in the treatment of chronic and habitual constipation, treatment of acute and the prevention and treatment of chronic Portal-systemic encephalopathy including the stages of hepatic pre-coma and coma.

Avolac is a hyperosmolar laxative which is used as an effective treatment approach for constipation. It is a non-absorbable disaccharide which draws water into the bowel; causes distention through fluid accumulation, thus promotes soft stool and accelerates bowel motion.

Avolac is also used to associated treatment for these conditions: Constipation, Hepatic Encephalopathy (HE)


Trade Name Avolac
Generic Lactulose
Lactulose Other Names Lactulosa, Lactulose, Lactulosum
Weight 3.35gm/5ml
Type Concentrated Oral Solution
Formula C12H22O11
Weight Average: 342.2965
Monoisotopic: 342.116211546
Protein binding

Negligible amounts of lactulose - metabolized or non-metabolized - are absorbed into the body.. Regardless, data regarding the protein binding of lactulose is not readily available or accessible.

Therapeutic Class Osmotic purgatives
Manufacturer Aristopharma Ltd
Available Country Bangladesh
Last Updated: June 23, 2021 at 11:22 am


Lactulose Structure


Avolac dosage

Adults (including elderly): 3 tea spoonful or 15 ml twice daily

Children 5 to 10 years: 2 tea spoonful or 10 ml twice daily

Children under 5 years: 1 tea spoonful or 5 ml twice daily

Babies under 1 year: ½ tea spoonful or 2.5 ml twice daily (paediatric dose should be given after breakfast)

Each dose of Avolac may, if necessary, be taken with water or fruit juices, usually once a day, preferably in the morning. If a dose is forgotten it should be taken as soon as one remembers up to 8 hours before bedtime. If later, wait for next scheduled dose (don’t double this dose). Don’t take at bedtime. Usual time lapse before drug works is 30 minutes to 3 hours.

Side Effects

Life threatening: None expected

Common: Increased thirst, cramps, nausea, diarrhoea, flatulence

Infrequent: Irregular heart beat, muscle cramps

Rare: Dizziness, confusion, fatigue, weakness.


It should be avoided if one is allergic to any hyperosmotic laxative, have symptoms of appendicitis, inflammatory bowel diseases or intestinal blockage, have missed a bowel movement for only 1 or 2 days. Adverse reactions over age 60 year may be more frequent and severe than in younger persons.


Reduced effect with non-absorbable antacids, neomycin and other oral anti-infectives. Concomitant use with other laxatives may falsely suggest that adequate lactulose dosage has been achieved.

Food Interaction

  • Drink plenty of fluids. This drug may cause fluid loss.
  • Take with or without food.

Volume of Distribution

Negligible amounts of lactulose - metabolized or non-metabolized - are absorbed into the body.. Most lactulose that is administered subsequently remains predominantly around the gastrointestinal tract area.

Half Life

The data regarding the half-life of lactulose is not readily available or accessible.


Negligible amounts of lactulose - metabolized or non-metabolized - are absorbed into the body.. Regardless, data regarding the clearance of lactulose is not readily available or accessible.

Pregnancy & Breastfeeding use

In pregnancy no proven problems were detected. Avoid the drug if possible. Consultation with physician is required. It has no side effect during breast feeding. Avolac oral solution could be used in infants and children only under medical supervision. It should not be used to ‘flush out’ the system or as a ‘tonic'.


Avolac is contraindicated in patients with galactosaemia and intestinal obstruction.

Acute Overdose

There have been no reports of accidental overdosage. In the event of acute overdosage it is expected that diarrhoea and abdominal cramps would be the major symptoms.

Storage Condition

Store between 15-30° C.

Innovators Monograph

Avolac contains Lactulose see full prescribing information from innovator Monograph