ICD-10 Specific code K59.0: Constipation

Bisacodyl is a locally acting laxative from the diphenylmethane derivatives group having a dual action. As a contact laxative, for which also antiresorptive hydragogue effects have been described, bisacodyl stimulates after hydrolysis in the large intestine, the mucosa of both the large intestine and of the rectum. Stimulation of the mucosa of the large intestine results in colonic peristalsis with promotion of accumulation of water, and consequently electrolytes, in the colonic lumen. This results in a stimulation of defecation, reduction of transit time and softening of the stool. Stimulation of the rectum causes increased motility and a feeling of rectal fullness. The rectal effect may help to restore the “call to stool” although its clinical relevance remains to be established.

Glycerol has uses as a hyperosmotic, osmotic diuretic, and ophthalmic agent. It may be used as an eye drop in the treatment of glaucoma to reduce intraocular pressure, as a solution or suppository for short-term treatment of constipation, to evacuate the bowel prior to a colonoscopy, and in some ocular surgeries. It may be given intravenously to reduce pressure inside the brain and used externally on the skin as a moisturizer.

Lactitol is a sugar alcohol used as a replacement bulk sweetener for low calorie foods with approximately 40% of the sweetness of sugar. Lactitol also promotes colon health as a prebiotic. Lactitol is a laxative and is used to prevent or treat constipation.

Lactulose is a synthetic disaccharide which is metabolised by gastro-intestinal bacterial flora to low molecular weight acids (chiefly lactic and acetic acids). There is no endogenous metabolising enzyme in the human gut. Its mode of action in constipation is as an osmotic agent producing soft stools.

High molecular weight (4000) macrogols are long linear polymers which retain water molecules by means of hydrogen bonds. When administered by the oral route, they lead to an increase in volume of intestinal fluids.

Magnesium hydroxide is practically insoluble in water and solution is not effected until the hydroxide reacts with hydrochloric acid in the stomach to form magnesium chloride. Its neutralising action is almost equal to that of sodium bicarbonate. When the dose is in excess of that required to neutralise the acid the intragastric pH may reach pH 8 or 9. Acid rebound following magnesium hydroxide is clinically insignificant. Magnesium hydroxide has an indirect cathartic effect resulting from water retention in the intestinal lumen.

The sugar moiety of the sennosides is removed by bacteria in the large intestine releasing the active anthrone fraction. This stimulates peristalsis via the submucosal and myenteric nerve plexuses.

Sodium picosulfate is a locally acting laxative from the triarylmethane group, which after bacterial cleavage in the colon, has a dual-action with stimulation of the mucosa of both the large intestine and of the rectum.