What is the appropriate dosing of lactulose for the treatment of constipation?

From the Guidelines

The recommended lactulose dosing for the treatment of constipation in adults is 10-20 grams (15-30 mL) daily, which may be increased to 40 grams (60 mL) daily if needed, as supported by the American Gastroenterological Association-American College of Gastroenterology clinical practice guideline 1.

Key Considerations

• Lactulose is a synthetic disaccharide that exerts an osmotic laxative effect in the colon to promote peristalsis.
• The dose may be adjusted based on individual response, with the goal of achieving 2-3 soft, formed stools per day.
• Common side effects of lactulose include bloating, gas, and abdominal cramps, which are dose-dependent and may limit its use in clinical practice 1.

Special Populations

• For children, the dosing is weight-based, but there is limited guidance in the provided evidence.
• Lactulose should be used cautiously in diabetics, as it may affect blood sugar levels.

Monitoring and Follow-up

• If constipation persists or worsens after 7 days of treatment, patients should consult a healthcare provider.
• Patients with galactosemia should not use lactulose, as it is contraindicated in this population.

Evidence Summary

The American Gastroenterological Association-American College of Gastroenterology clinical practice guideline recommends lactulose as a treatment option for chronic idiopathic constipation (CIC) in adults who fail or are intolerant to over-the-counter (OTC) therapies, with a conditional recommendation and very low certainty of evidence 1. However, the guideline also notes that bloating and flatulence are common side effects of lactulose, which may limit its use in clinical practice. Overall, the evidence supports the use of lactulose as a treatment option for constipation, with careful consideration of individual patient factors and potential side effects.

From the FDA Drug Label

The usual adult, oral dosage is 2 to 3 tablespoonfuls (30 mL to 45 mL, containing 20 grams to 30 grams of lactulose) three or four times daily. The dosage may be adjusted every day or two to produce 2 or 3 soft stools daily Pediatric: ...the recommended initial daily oral dose in infants is 2. 5 mL to 10 mL in divided doses. For older children and adolescents the total daily dose is 40 mL to 90 mL.

The appropriate dosing of lactulose for the treatment of constipation is:

• Adults: 2 to 3 tablespoonfuls (30 mL to 45 mL) three or four times daily, adjusted to produce 2 or 3 soft stools daily
• Pediatric:
  • Infants: 2.5 mL to 10 mL in divided doses
  • Older children and adolescents: 40 mL to 90 mL total daily dose 2

From the Research

Dosing of Lactulose for Constipation

• The appropriate dosing of lactulose for the treatment of constipation is typically in the range of 10-20 g per day 3.
• A study found that ingestion or intracolonic infusion of 15 g lactulose significantly decreased barostat bag volume and accelerated isotopic colonic transit time compared to a control group 3.
• Another study compared the efficacy and safety of lactitol versus lactulose in the management of constipation, and found that lactitol was comparable to lactulose in terms of normal consistency of stool and number of bowel movement per week, but had better acceptance and compliance by patients 4.
• The dose of lactulose required for pediatric patients was found to be 500-750 mg/kg/day, while lactitol required a dose of 250-400 mg/kg/day 4.
• A study comparing lactulose syrup to a placebo found that lactulose produced clinically and statistically significant increases in the frequency, weight, volume, and water content of stools, and produced stools of softer consistency compared to baseline values 5.
• The laxative effects of lactulose were found to be dose-related, with a higher dose of 60 ml/day producing greater effects than a lower dose of 30 ml/day 5.
• A comparison of lactulose with polyethylene glycol (PEG) 3350 found that PEG was more effective than lactulose in treating chronic constipation, with a higher number of stools and lower median daily score for straining at stool 6.
• A study on the laxative effect and tolerance of lactulose administered in one or two intakes found that the effects and tolerance of lactulose were equivalent whether taken in one or two intakes, with a daily dose of 20 g 7.