Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Osmotically acting laxatives.
ATC code: A06A D11
Lactulose is a synthetic disaccharide formed from D-galactose and fructose. In the colon lactulose is metabolised by bacterial enzymes to short chained fatty acids mainly lactic and acetic acid as well as methane and hydrogen. This effect leads to a decrease of the pH-value and an increase of the osmotic pressure in the colon. This causes stimulation of peristalsis and an increase of the water content of the faeces.

In higher dosage lactulose causes a reduction of the pH-value, which results in an increased H+-concentration and a shift from NH3 (absorbable) to NH4+ (non-absorbable). The nitrogen excretion in the stool is accelerated. This effect may be used in the treatment of hyperammonaemia. In the treatment of hepatic encephalopathy lactulose reduces the concentration of NH3 in the blood by about 25-50 %.

Lower pH in the colon leads to suppression of proteolytic bacteria, which are involved in the formation of ammonia. Decrease in pH is caused by increasing the content of acidophilic bacteria (eg Lactobacillus). Reduced pH and the osmotic effect cleanse the colon; this stimulates the bacteria to use ammonia for bacterial protein synthesis.

Pharmacokinetic Properties

5.2 Pharmacokinetic properties
Lactulose is practically not absorbed, because in man there is no corresponding disaccharidase available in the upper intestinal tract. Not being absorbed as such, it reaches the colon unchanged. There it is metabolised by the colonic bacterial flora. Metabolism is complete at doses up to 25-50 g or 40-75 ml; at higher dosages, a proportion may be excreted unchanged.