Faeces laxatives

This is a semisynthetic disaccharide which is not absorbed from the GI tract. It produces an osmotic diarrhoea of low pH, and discourages the proliferation of ammonia-producing bacteria. It is therefore useful in the treatment of hepatic encephalopathy. Osmotic laxatives like lactulose, sorbitol, and lactilol rarely cause significant adverse effects. Glycerol suppositories are useful in softening and lubricating passage of inspissated faeces. 

Constipation is the infrequent or difficult evacuation of faeces. There is no exact definition, but it is a reduction in normal stool frequency accompanied by hardening of stools. Constipation that is not secondary to underlying disease or caused by factors such as side-effects of drugs or laxative abuse is known as simple or functional constipation and may be self-treated with advice from a pharmacist. 

Faecal softeners act as detergents on the surface of faeces causing them to absorb water and soften. An example is docusate, which can be used prior to imaging. However, other types of laxatives (see below) are better for this purpose. 

Lubricants work by coating the faeces and rectal wall, thereby aiding expulsion of faeces. A traditional example of a lubricant laxative is liquid paraffin. Lubricants do not work fast enough to be useful prior to radiological imaging. 

Provided thatdietary input is adequate, the presence of malabstirption from the small bowel will often be indicated by changes in the faeces, in particular by diarrhoea. Diarrhoea due to malabsorption can be assumed only if other cau.ses, such as infection and laxative abuse, have been... 

The hygroscopic nature of polyols makes them effective osmotic laxatives since they retain water in the bowel thus softening faeces. Hie polyol, lactitol (Fig. 5.7), is even more effective for this purpose since it is not absorbed by the intestine and passes straight through to the bowel. Mannitol is used in infusions in order to treat cerebral oedema by drawing water away from brain tissue, e.g. due to the effects of high altitude. 

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