Lactulose

Class	Osmotic laxative
Chemistry	Disaccharide of glucose and fructose
Routes of administration	Oral, rectal (as enema)
Absorption	Non-absorbable
Solubility	pKa 10.28; highly water-soluble
Distribution	Not absorbed; remains in the bowel
Metabolism	Undergoes metabolism by gut bacteria only
Elimination	Eliminated in the stool, as metabolic byproducts, gas, and unchanged drug
Time course of action	Elimination half-life is about 2 hours; duration of effect may be up to 4-8 hours
Target receptor	Does not bind to any receptors
Mechanism of action	By increasing the osmolality of stool, increases the water content of stool (i.e. prevents the reabsorption of water in the bowel). Also, by acting as a metabolic substrate, has the effect of diverting bacterial metabolism to the production of non-nitrogenous metabolites, which is beneficial in hepatic encephalopathy
Clinical effects	Abdominal distension, flatulence, water loss though diarrhoea, electrolyte derangement, volume depletion, malabsorption of nutrients
Literature reference	Clausen et al (1997)
CICM details of understanding	Not specifically listed in the CICM syllabus
Mentioned around Deranged Physiology
Related SAQs