Faeces softeners

These drugs act to increase the volume of stool by absorbing water and as a result softening of faeces occurs. These are safe drugs (except in patient with strictures when intestinal obstruction may be precipitated). Adequate hydration of the patient is to be maintained. The onset of action occurs in 12-24 hours after oral intake. 

It is a petroleum hydrocarbon, an inert viscous liquid. It is a faecal softener and causes lubrication of hard scybali by coating them. Paraffin lubricates the passage of faeces. It is not absorbed and is safe. 

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. 

Docusate sodium (dioctyl sodiirai sulphosuccinate) softens faeces by lowering the surface tension of fluids in the bowel. This allows more water to remain in the faeces. It appears also to have bowel stimulant properties but these are relatively weak. Docusate sodium acts in 1-2 days. Poloxamers, e.g. poloxalkol (poloxamer 188), act similarly and are used in combination with other agents. 

Suppositories (bisacodyl, glycerin) may be used to obtain a bowel action in about 1 hour. Enemas produce defaecation by softening faeces and distending the bowel. They are used in preparation for surgery, radiological examination and endoscopy. Preparations with sodium phosphate, which is poorly absorbed and so retains water in the gut, are generally used. Arachis oil is included in enemas to soften impacted faeces. 

It is indigestible and absorbed only to a small extent. It penetrates and softens faeces, coating the surface with an oily film that facilitates its passage through the intestine. 

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. 

Faecal softeners pnrmote defaecaliun by softening (e.g. docusate and/or lubricating (e.g. arachis oil, lit uid paraflin) faeces and assisting evacuation. Chronic use of liquid paraffin may impair absorption of the fat-soluble vitamins A and D and cause paraffinomas. 

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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