Lilac Mechanism of Action

Laxative.
Pharmacology: Mechanism of Action: Two mechanisms are believed to be involved in the laxative action of lactulose: First, metabolism of lactulose by bacteria results in reduced colonic pH which stimulates peristalsis and decreases stool transit time. In turn, decreased water reabsorption from the feces further facilitates the passage of soft well-formed stools. Second, increased osmotic pressure of fecal material secondary to an increase in colonic organic acids results in accumulation of fluid from surrounding tissues, helping to soften stool mass.
The therapeutic action of lactulose in ameliorating the symptoms of hepatic encephalopathy is considered to be a result of the following: Reduction of fecal pH leading to a reduced ammonia absorption via non-ionic diffusion and/or diffusion of ammonia from the blood into the gut. The trapped ammonia is then excreted in the stools; suppression of urase-producing organisms; induction of an osmotic type of diarrhea which diminishes fecal stasis with reduction of nitrogenous substances for ammonia production. Decreased absorption of ammonia from the gut also results from shortening intestinal transit time.
The actual mechanism may be a combination of these effects.
Pharmacokinetics: Absorption: Lactulose is poorly absorbed from the GIT and no enzyme capable of hydrolysis of this disaccharide is present in human GI tissue. As a result, oral doses of lactulose reach the colon virtually unchanged.
Less than 2% of lactulose is absorbed systematically. Absorption may be enhanced 4- to 6-fold by increasing the osmotic value of the intestinal contents.
Distribution: Lactulose given orally resulted in only small amounts reaching the blood.
Metabolism and Elimination: Following administration by mouth, lactulose passes essentially unchanged into the large intestine where it is metabolized by saccharolytic bacteria with the formation of simple organic acids, mainly lactic acid and small amounts of acetic and formic acids. The small amount of absorbed lactulose is subsequently excreted unchanged in the urine. Urinary excretion has been determined to be ≤3% and is essentially complete within 24 hrs.