Laxatives are also called as aperient. These laxatives promote evacuation bowels. They are milder in action. The frequency and volume of faeces is regulated by the diet. Constipation is characterised by infrequent evacuation of bowels, hard and dry faeces. It may also cause discomfort, malaise and loss of apetite. They are classified in to the following,
BULK LAXATIVES: increase the volume of the intestinal contents, stimulating Peristalsis. They include,
Bran:
Increasing the intake of dietary fibres like bran is the first line approach in the treatment of constipation in most cases. It contains unabsorbable cellulose, pectins, glycoproteins and other polysaccharides. It absorbs water in the intestines, swells, increases water content of faeces thus softening the faeces. It facilitates bacterial growth in the Colon which increases the faecal mass.
Methyl cllulose:
It is a semisynthetic, colloidal, hydrophillic derivative of cellulose. Around 4-6 grams per day is effective in most cases. It absorbs water thus increasing the bulk of the faeces. large amounts of water must be taken along with these bulk forming agents.
Lactulose:
This is an osmotic laxative which increases bulk in the bowel and by retaining water by an osmotic effect. It is a semisyntetic disaccharide of Fructose and Lactose. It is broken down in the colon by bacteria to osmotically more active products. a dose of 10 gram, twice daily is effective in most cases. Plenty of water has to be taken along with lactulose.
STIMULANT LAXATIVES: increase motility by acting on the Mucosa or nerve plexuses, which may be damaged by prolonges use. They often cause abdominal cramps. They include,
Anthraquinones:
These are rich in senna leaves obtained from cassia senna and other cassia species. Senna is commonly used. It contains anthraquinone glycosides. It is inactive as such. It is unabsorbable in small intestine, when it reaches colon bacteria liberate the anthranol form which act locally or absorbed in to circulation. It is believed to act on the myenteric plexus and increase peristalsis.
FAECAL SOFTENERS: promote defecation by sofening and /or lubricating faeces and assisting evacuation of bowel. they include,
Liquid paraffin:
It is a viscous liquid. It is mixture of petroleum hydrocarbons. It was introduced as a laxative at the turn of 19 th century. Millions of gallons have passed through the intestinal pipeline since then. When taken for 2 to 3 days, it softens stools and is said to lubricate hard scybali by coating them. Chronic use of liquid paraffin impair absorption of fat soluble vitamins A and D and cause paraffinomas.
Docusates:
It is an annionic detergent. It emusifies the colonic contents and increases penetration of water in to faeces. By ites detergent action, it can disrupt the mucosal barrier and enhance absorption of nonabsorbable drugs, e.g. liquid paraffin. because of this effect liquid paraffin should not be combined with Docusates. It causes abdominal pain and cramps. It may cause Hepatotoxicity on prolonged use.
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