How is lactulose taken?

How Lactulose is Taken

Lactulose is taken orally as a liquid solution, with dosing that varies by indication: for constipation, start with 15-30 mL (10-20 g) daily as a single evening dose, while for hepatic encephalopathy, use 30-45 mL (20-30 g) three to four times daily, titrated to produce 2-3 soft bowel movements per day. 1, 2, 3

Administration Routes and Methods

Oral Administration (Preferred Route)

• The standard oral dose for adults is 2-3 tablespoonfuls (30-45 mL) containing 20-30 grams of lactulose, taken three or four times daily 3
• The medication comes as a liquid solution that can be measured using the provided measuring device 3
• For constipation specifically, taking lactulose as a single evening dose optimizes compliance and minimizes side effects 4

Rectal Administration (When Oral Route Not Feasible)

• When patients cannot take oral medications due to impending coma, coma stage, or risk of aspiration, lactulose can be given as a retention enema 1, 3
• Mix 300 mL of lactulose solution with 700 mL of water or physiologic saline, and retain in the intestine for 30-60 minutes 1, 3
• The enema can be repeated every 4-6 hours if needed 3
• Avoid using cleansing enemas with soap suds or alkaline agents before lactulose administration 3

Dosing by Indication

For Chronic Constipation

• Initial dose: 10-20 g (15-30 mL or 1-2 packets) daily 2, 4
• Maximum dose: 40 g (60 mL or 2-4 packets) daily if needed 2
• Adjust dosing every day or two to produce 2-3 soft stools daily 3

For Hepatic Encephalopathy

• Acute phase: 30-45 mL every 1-2 hours until at least 2 soft bowel movements are produced 1, 2, 3
• Maintenance: 20-30 g (30-45 mL) three to four times daily 1, 2
• Goal is to maintain 2-3 soft stools per day 1, 2
• Improvement may occur within 24 hours but can take 48 hours or longer 3

Pediatric Dosing

• Infants: 2.5-10 mL daily in divided doses 3
• Older children and adolescents: 40-90 mL total daily dose 3
• If diarrhea occurs, reduce dose immediately; if it persists, discontinue lactulose 3

Critical Dosing Considerations and Pitfalls

Common Side Effects to Monitor

• Bloating and flatulence are dose-dependent and occur in approximately 20% of patients, which may limit use 4
• Abdominal pain and cramps are common side effects 4
• Starting with lower doses and increasing as tolerated minimizes gastrointestinal side effects 4

Serious Complications to Avoid

• Excessive dosing can cause dehydration, hypernatremia (high sodium), and hypokalemia (low potassium) 2, 4
• Severe perianal skin irritation can occur with overuse 1, 2
• In hepatic encephalopathy patients, paradoxically, excessive use may precipitate encephalopathy 1, 2
• If excessive bowel movements occur (>2 per day), reduce the dose immediately 2

Timing and Onset of Action

• The laxative effect typically begins within 24-48 hours of starting therapy 3
• For hepatic encephalopathy, reversal of coma may occur within 2 hours of the first enema in some patients 3
• Continuous long-term therapy is indicated for hepatic encephalopathy to prevent recurrence 3