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lactulose 10 gm/15 ml solution (generic enulose, generlac)

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Portal-Systemic Encephalopathy

Lactulose is used as an adjunct to protein restriction and supportive therapy for the prevention and treatment of portal-systemic encephalopathy (PSE) including hepatic pre-coma and coma. Lactulose has been useful in the management of PSE resulting from surgical portacaval shunts or from chronic hepatic diseases such as cirrhosis. In patients with PSE, lactulose therapy reduces the blood ammonia concentration and this is usually accompanied by substantial improvement in the mental state of the patient and improved EEG tracings. Many patients are able to tolerate increased dietary protein during lactulose therapy. The drug does not, however, alter the course of the underlying liver disease. Therefore, use of lactulose in the treatment of PSE does not obviate treatment of underlying liver disease, nor preclude other measures used in the treatment of PSE.

A good clinical response has been achieved in 75-85% of PSE patients receiving lactulose therapy. Because lactulose is relatively nontoxic, it is a valuable alternative to antibiotics such as neomycin, especially when prolonged therapy is required or when neomycin is contraindicated. Some well-controlled comparative studies have shown that the efficacy of lactulose is superior to that of laxative controls (such as magnesium sulfate or sorbitol) and about equal to that of neomycin in the treatment of acute and chronic PSE. Some patients who had previously failed to respond to neomycin and dietary protein restriction responded to lactulose therapy. Conversely, other patients responded better to neomycin than to lactulose.

Since neomycin destroys bacteria and lactulose requires bacterial degradation for its effectiveness, concomitant therapy with these agents is theoretically counterproductive. (See Drug Interactions: Anti-infective Agents.) It appears, however, that lactulose remains active when administered with neomycin and, in fact, there is some evidence that concomitant therapy with lactulose and neomycin may be more effective than either drug alone. Some clinicians recommend neomycin for acute episodes of PSE and lactulose for the long-term management of chronic PSE.

Lactulose is not useful in the management of non-nitrogenous types of encephalopathy such as those induced by drugs or metabolic or electrolyte disturbances. Lactulose therapy is not effective in the treatment of coma associated with infectious hepatitis or other acute disorders of the liver. In a case of hyperammonemia, which was apparently caused by an inborn error of metabolism, lactulose therapy was ineffective.


Lactulose is useful as a laxative in the treatment of chronic constipation in adults and geriatric patients. The drug has been used in the treatment of chronic constipation in children; however, the manufacturers state that safety and efficacy of lactulose for the treatment of chronic constipation in children have not been established. Lactulose has also been used to restore regular bowel movements in hemorrhoidectomy patients. Following a barium meal examination, the drug has been used to induce bowel evacuation in geriatric patients with colonic retention of barium and severe constipation. Although lactulose is effective in the treatment of chronic constipation, its superiority to conventional laxatives has not been established.

Dosage and Administration

Reconstitution and Administration

Lactulose is usually administered orally. The sweet taste of lactulose solution, which may be unpleasant to some patients, can be minimized by diluting the solution with water, fruit juice, or milk or administering it in food such as desserts. When lactulose solution is administered via a gastric tube, it should be well diluted to prevent induction of vomiting and the possibility of aspiration pneumonia.

Lactulose may also be administered rectally to adults with portal-systemic encephalopathy (PSE) during stages of hepatic pre-coma or coma when the possibility of aspiration exists, or when necessary endoscopic or intubation procedures interfere with oral administration.

For oral administration, lactulose powder should be reconstituted by dissolving the contents of a packet labeled as containing 10 or 20 g of the drug in approximately 120 mL of water.


Each 15 mL of commercially available lactulose solution provides approximately 10 g of the drug; corresponding doses provided by 2.5, 5, 7.5, 10, 30, 40, 45, 90, 150, and 300 mL of the commercial solution are approximately 1.67, 3.3, 5, 6.67, 20, 27, 30, 60, 100, and 200 g, respectively. Following reconstitution of the oral powder as directed, a 10 or 20 g dose is provided by the total volume.

Portal-Systemic Encephalopathy

For the prevention and treatment of PSE in adults, the usual initial oral dosage of lactulose is 20-30 g 3 or 4 times daily. Dosage is then adjusted every 1-2 days as necessary to produce 2 or 3 soft stools daily. Some clinicians recommend that dosage be adjusted according to the acidity of the colonic contents by measuring stool pH (with indicator paper) at the start of therapy and adjusting the dosage until stool pH is about 5. This pH is usually achieved when the patient has 2 or 3 soft stools daily during lactulose therapy. For most adults, lactulose dosage is usually 60-100 g daily, although some patients may require higher dosage.

In the management of acute episodes of PSE in adults, 20-30 g may be given orally at 1- to 2-hour intervals to induce rapid laxation. When the laxative effect has been achieved, the dose of lactulose is reduced to the amount required to produce 2 or 3 soft stools daily. When lactulose is administered in the treatment of PSE, improvement in the clinical condition of the patient usually occurs within 1-3 days. Continuous long-term therapy with lactulose may decrease the severity and prevent the recurrence of PSE.

Based on limited information, the initial oral dosage of lactulose for the prevention and treatment of PSE in infants is 1.67-6.67 g daily given in divided doses. In older children and adolescents, the total daily dose of lactulose suggested by the manufacturers is 27-60 g. Dosage is adjusted every 1-2 days as necessary to produce 2-3 soft stools daily. If the initial dose of lactulose produces diarrhea, the dose should be reduced immediately; if diarrhea persists, the drug should be discontinued.

When lactulose is used rectally in the treatment of PSE to reverse hepatic coma in adults, 200 g is diluted with 700 mL of water or 0.9% sodium chloride solution; the diluted solution is administered rectally via a rectal balloon catheter and retained for 30-60 minutes. Lactulose retention enemas may be administered every 4-6 hours; if the enema is retained for less than 30 minutes, it may be repeated immediately. In some patients, reversal of hepatic coma may occur within 2 hours of the first enema. Before discontinuance of lactulose retention enemas, recommended oral dosages of the drug should be started. Cleansing enemas containing soapsuds or other alkaline agents should not be used concomitantly with lactulose enemas.


For the treatment of chronic constipation in adults, the usual initial dosage of lactulose is 10-20 g daily. Dosage may be increased to 40 g daily if necessary. Following oral lactulose administration, 24-48 hours may be required to restore normal bowel movements.

For the treatment of chronic constipation in children, lactulose dosages of least 5 g daily, usually given as a single dose after breakfast, have been used. When lactulose was used to restore bowel movements in hemorrhoidectomy patients, a 10-g dose was given twice during the day before surgery and twice daily for 5 days postoperatively. To induce bowel evacuation in geriatric patients with colonic retention of barium and severe constipation following a barium meal examination, lactulose dosages of 3.3-6.7 g twice daily for 1-4 weeks have been used.


Adverse Effects

During the first few days of therapy, lactulose frequently produces gaseous distention, belching, flatulence, borborygmi, and/or abdominal discomfort such as cramping. These adverse effects usually subside with continued therapy, but dosage reduction may be required. Diarrhea indicates overdosage and responds to dosage reduction. Potential complications of diarrhea include fluid loss, hypokalemia, and hypernatremia. Infants receiving lactulose may develop dehydration and hyponatremia. Nausea and vomiting have been reported infrequently in patients receiving the drug.

Precautions and Contraindications

In the treatment of PSE, it is important to remember that the serious underlying liver disease may produce complications such as electrolyte disturbances (e.g., hypokalemia) which require additional therapy. In addition, if diarrhea occurs it may severely deplete fluids and potassium and may intensify symptoms of PSE. For these reasons, some clinicians recommend periodic determinations of serum potassium concentrations during long-term treatment with lactulose.

Lactulose solution should be administered with caution to patients who may require electrocautery procedures during proctoscopy or colonoscopy, since the drug can cause accumulation of hydrogen gas in high concentrations which in the presence of an electrical spark may theoretically result in an explosive reaction. Although this reaction has not been reported to date, patients receiving lactulose therapy should have a thorough bowel cleansing with a nonfermentable solution prior to these procedures. In addition, insufflation of carbon dioxide may be used but is probably an unnecessary measure.

If an unusual diarrheal condition occurs during lactulose therapy, patients should contact their physician. Geriatric, debilitated patients who receive lactulose for more than 6 months should have serum electrolytes (e.g., potassium, chloride, carbon dioxide) measured periodically during therapy.

Since lactulose solution contains some free lactose and galactose, the drug should be used with caution in patients with diabetes mellitus and is contraindicated in patients who require a low-galactose diet.

Laxatives should not be administered with lactulose. (See Drug Interactions: Laxatives.)

Pediatric Precautions

Limited information on the use of lactulose for prevention and treatment of PSE in young children and adolescents is available. Safety and efficacy of the drug for the treatment of chronic constipation in children have not been established.

Mutagenicity and Carcinogenicity

Data on the long-term mutagenic potential of lactulose in animals or humans and on the long-term carcinogenic potential in humans are not available. Administration of lactulose solution in concentrations of 3 and 10% v/w in the diet of mice for 18 months did not produce evidence of carcinogenicity.

Pregnancy, Fertility, and Lactation


Use of lactulose during pregnancy has not been studied in humans. Reproduction studies in rats, mice, and rabbits receiving oral lactulose doses up to 6 times the usual human oral dose have not revealed evidence of harm to the fetus. Lactulose should be used during pregnancy only when clearly needed.


Reproduction studies in rats, mice, and rabbits using oral lactulose dosages of up to 4 or 8 g/kg (6 or 12 mL/kg) daily did not reveal evidence of impaired fertility.


It is not known if lactulose is distributed into milk. The drug should be used with caution in nursing women.

Drug Interactions


Additional laxatives should not be administered with lactulose solution, especially when lactulose therapy is initiated, because the loose stools produced may be falsely interpreted as an indication that adequate dosage of lactulose has been achieved.

Anti-infective Agents

Theoretically, orally administered neomycin and possibly other anti-infective agents, when administered concurrently with lactulose, could eliminate colonic bacteria that are necessary to metabolize lactulose and thereby prevent acidification of the contents of the colon. Limited data obtained from experiments in healthy individuals tend to support the theoretical incompatibility of these agents. There is, however, evidence that lactulose remains active when administered with neomycin to patients with PSE. In addition, there have been reports that concomitant therapy with lactulose and neomycin may be more effective than either drug alone in the treatment of PSE. Therefore, until there is conclusive evidence that concurrent administration of lactulose and neomycin or other oral anti-infective agents is efficacious, patients receiving lactulose and an oral anti-infective agent should be closely monitored for possible inadequate response to lactulose.


Results of limited studies in rats and humans suggest that nonabsorbable antacids administered concomitantly with lactulose may inhibit the desired decrease in fecal pH in the colon. The potential lack of desired effect of lactulose should be considered before a nonabsorbable antacid is administered concomitantly with lactulose.


Following oral administration, less than 3% of a dose of lactulose is absorbed from the small intestine. Absorbed lactulose is not metabolized and is excreted in the urine unchanged within 24 hours. Unabsorbed lactulose reaches the colon unchanged where it is metabolized by bacteria to form lactic acid and small amounts of acetic and formic acids. The bacteria normally present in the colon which are capable of metabolizing lactulose include Lactobacilli, Bacteroides, Escherichia coli, and Clostridia, but not Proteus mirabilis, Enterococcus faecalis (formerly Streptococcus faecalis), Salmonella, or Shigella. Only negligible amounts of lactulose or its metabolites are absorbed from the colon.

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