Drugs or other substances used to treat CONSTIPATION. Also called aperients or purgatives, laxatives are classi?ed according to their mode of action. The four main groups are bulk, stimulant, faecal softeners and osmotics. In addition, bowel-cleansing solutions are used before surgery, ENDOSCOPY, or radiological examination of the COLON, to ensure that the bowel is clear of solid matter. However, these are not procedures for treating constipation.
People should be aware that normal bowel habits vary greatly, from twice a day to once every two or even three days. Any change from normal frequency to irregular or infrequent defaecation may signal constipation. Furthermore, before laxatives are prescribed, it is essential to ensure that the constipation is not the result of an underlying condition producing ‘secondary’ constipation. Individuals should not use laxatives too often or indiscriminately; persistent constipation is a reason to seek medical advice.
Bulk laxatives include bran and most high-?bre foods, such as fruit, vegetables and wholemeal foods. These leave a large indigestible residue that holds water in the gut and produces a large soft stool. Isphaghula husk, methyl cellulose and stercula are helpful when bran is ine?ective. Inorganic salts such as magnesium sulphate (Epsom Salts) have a similar e?ect.
Stimulant laxatives – for example, bisacodyl, senna and docusate sodium – stimulate PERISTALSIS, although the action may be accompanied by colicky pains.
Faecal softeners (emollients) There are two groups: surface active agents such as dioctyl sodium and sulphosuccinate which retain water in the stools and are often combined with a stimulant purgative; and liquid para?n which is chemically inert and is said to act by lubrication.
Osmotic laxatives These substances act by holding ?uid in the bowel by OSMOSIS, or by altering the manner in which water is distributed in the FAECES. Magnesium salts are used to produce rapid bowel evacuation, although one of them, magnesium hydroxide, should be used only occasionally. Phosphate or sodium citrate enemas (see ENEMA) can be used for constipation, while the former is used to ensure bowel evacuation before abdominal radiological procedures, endoscopy and surgery.... laxatives
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