Lactulose Dosage and Treatment Protocol for Constipation
For treating constipation in adults, the recommended lactulose dosage is 15-30 mL (10-20g) once daily, preferably at night, which can be increased to 60 mL (40g) daily if needed. 1 This osmotic laxative works by drawing water into the intestinal lumen, producing softer stools and facilitating bowel movements.
Adult Dosing Protocol
Initial Dosing
- Start with 15-30 mL (10-20g) once daily, preferably at night 1
- Alternative FDA-approved dosing: 30-45 mL (20-30g) three to four times daily 2
- Allow 24-48 hours for initial response 2
Dose Titration
- If initial dose is insufficient, increase to 40g (60 mL) daily 1
- Adjust dose every 1-2 days to achieve 2-3 soft stools daily 2
- Consider dividing into two doses if single dose causes excessive bloating 1
Maintenance
- Continue at lowest effective dose that maintains 2-3 soft bowel movements daily
- Evaluate treatment response every 4-6 weeks 1
- Long-term therapy is safe when properly monitored 1
Pediatric Dosing
- Infants: 2.5-10 mL daily in divided doses 2
- Older children and adolescents: 40-90 mL total daily dose 2
- Reduce dose immediately if diarrhea occurs 2
- Discontinue if diarrhea persists 2
Administration Tips
- Take with adequate fluid intake to optimize effect 1
- Starting with lower doses and gradual titration improves tolerability 1
- Consider taking with meals to minimize gastrointestinal side effects
Monitoring
- Monitor electrolytes periodically, especially with higher doses 1
- Assess hydration status regularly, particularly in elderly patients 1
- If no response within 48 hours, consider adding a stimulant laxative 1
Side Effects and Precautions
- Common side effects: bloating and flatulence (dose-dependent) 1
- Risk of diarrhea and electrolyte disturbances with high doses 1
- Contraindicated in patients with galactosemia 1
- Elderly patients may be more susceptible to dehydration 1
- Generally safe in pregnancy and diabetes 1
Clinical Evidence and Considerations
- Studies show lactulose produces clinically significant increases in stool frequency, weight, volume, and water content compared to placebo 3
- Laxative effects appear to be dose-related 3
- Lactulose has been shown effective for special populations including postpartum women 4 and patients with medication-induced constipation 5
- Single daily dosing (20g) in the evening has been shown to be as effective as divided doses with equivalent tolerance 6