Lactulose (Hepatic Encephalopathy)

How it works

Colonic fermentation of lactulose acidifies the bowel contents, which traps ammonia as ammonium and reduces its absorption while increasing gut transit, thereby lowering blood ammonia and the nitrogenous load driving encephalopathy.

Prescribing in practice

• Titrate the dose to achieve the target of a small number of soft stools each day, as this is the therapeutic endpoint in encephalopathy rather than simply relieving constipation.
• Excessive use can cause diarrhoea with dehydration and electrolyte disturbance, which may itself precipitate or worsen encephalopathy, so balance is essential.
• It may be given by mouth or, in patients unable to swallow safely, rectally, and is often combined with rifaximin for recurrent episodes.

Monitoring

Monitor stool frequency and the patient's conscious level and mental state, adjusting the dose to the target number of soft stools daily while watching fluid and electrolyte balance.

Counselling the patient

• The dose is adjusted to give a set number of soft stools a day, which helps clear the toxins affecting the brain.
• Carers should report increasing confusion or drowsiness, and seek advice if stools become very loose.

Evidence & guidelines

Lactulose is the established first-line therapy for the treatment and secondary prevention of hepatic encephalopathy in chronic liver disease.