What is the recommended dose of lactulose (lactulose) syrup for constipation and hepatic encephalopathy?

Lactulose Dosing for Constipation and Hepatic Encephalopathy

For hepatic encephalopathy, start with 25-30 mL of lactulose syrup every 1-2 hours until at least two soft bowel movements are produced daily, then titrate to maintain 2-3 soft bowel movements per day. 1, 2, 3

Dosing for Hepatic Encephalopathy

Initial Dosing

• For acute hepatic encephalopathy, administer 30-45 mL (20-30 g) of lactulose every 1-2 hours orally until at least 2 soft bowel movements are produced daily 2, 3
• European guidelines specifically recommend 25 mL of lactulose syrup every 1-2 hours until achieving at least two soft or loose bowel movements per day 1, 2
• Hourly doses may be used to induce rapid laxation in the initial phase of therapy 3

Maintenance Dosing

• After initial response, titrate to 20-30 g (30-45 mL) administered 3-4 times daily to maintain 2-3 soft stools per day 2, 3
• The FDA-approved maintenance dosage is 2-3 tablespoonfuls (30-45 mL) three or four times daily 3
• Dosing should be adjusted every day or two to achieve the target of 2-3 soft stools daily 3

Rectal Administration for Severe Cases

• For patients with severe hepatic encephalopathy (grade 3 or higher) or those unable to take oral medications, administer 300 mL lactulose mixed with 700 mL water as a retention enema 2, 3
• Retention enema should be retained for 30-60 minutes and may be repeated every 4-6 hours 3
• Cleansing enemas containing soap suds or other alkaline agents should not be used 3

Dosing for Constipation

• Initial recommended dose for chronic idiopathic constipation is 10-20 g (15-30 mL) daily 4
• Maximum dose for constipation is 40 g (60 mL) daily 4

Important Considerations and Pitfalls

Avoiding Overuse

• It is a misconception that lack of effect from smaller amounts of lactulose is remedied by much larger doses 1
• Overuse of lactulose can lead to serious complications, including:
  • Aspiration
  • Dehydration
  • Hypernatremia
  • Severe perianal skin irritation
  • Paradoxical precipitation of hepatic encephalopathy 1, 2, 4

Monitoring and Adjustments

• The goal of treatment is to achieve 2-3 soft bowel movements per day 1, 2, 4
• Improvement in hepatic encephalopathy may occur within 24 hours but may not begin before 48 hours or even later 3
• Continuous long-term therapy is indicated to lessen the severity and prevent recurrence of portal-systemic encephalopathy 3
• Doses should be reduced if excessive bowel movements occur (>2 per day) 4

Pediatric Dosing

• For infants: 2.5-10 mL in divided doses daily 3
• For older children and adolescents: 40-90 mL total daily dose 3
• If initial dose causes diarrhea, reduce immediately; if diarrhea persists, discontinue lactulose 3

Efficacy

• Clinical studies have shown that lactulose leads to recovery in 70-90% of hepatic encephalopathy patients 2
• Psychometric performance improves consistently during treatment with lactulose in patients with subclinical hepatic encephalopathy 5