lactulose
Brand: Kristalose, Enulose
Prototype Drug
Drug Class: laxative (osmotic) / hyperammonemia treatment
Drug Family: GI agent
Subclass: disaccharide osmotic agent
Organ Systems: gastrointestinal
Mechanism of Action
Non-absorbable disaccharide metabolized by colonic bacteria to lactic and acetic acid; osmotic effect draws water into lumen; acidification of colon traps ammonium (NH4+) reducing absorption in hepatic encephalopathy.
colonic bacteria (metabolizes to organic acids)
Indications
- constipation (chronic)
- hepatic encephalopathy (prevention and treatment)
- portal systemic encephalopathy
Contraindications
- galactosemia
- bowel obstruction
Adverse Effects
Common
- flatulence
- bloating
- cramping
- diarrhea
Serious
- severe electrolyte disturbances (overdose)
- aspiration risk
Pharmacokinetics (ADME)
| Absorption | minimal absorption |
| Distribution | colonic lumen |
| Metabolism | colonic bacteria to lactate, acetate, formate |
| Excretion | fecal |
| Half-life | not applicable |
| Onset | 24-48 hours (constipation) |
| Peak | 24-48 hours |
| Duration | variable |
| Protein Binding | none |
| Vd | none |
Nursing Considerations
- Hepatic encephalopathy: titrate dose to 2-3 soft stools per day
- Lactulose enema: 300 mL in 700 mL water for acute hepatic encephalopathy if oral not possible
- Monitor for electrolyte disturbances with high doses
- Can mix with juice or water to improve taste (sweet syrup)
Clinical Pearls
- Dual mechanism in hepatic encephalopathy: osmotic laxative reduces gut transit + acidification traps NH3 as NH4+ reducing absorption
- Titrate to 2-3 stools/day — too few bowel movements means under-treated, too many risks dehydration
Safety Profile
Pregnancy safe
Lactation generally-safe
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.