senna, docusate sodium)
■ Bulk forming laxatives (ispaghula husk) ■ Faecal so eners (docusate sodium).
ere are many similarities between the classes
in terms of metabolism and side-e ects. In general, laxatives, regardless of class, are not appreciably absorbed from the gastrointestinal tract except senna, which is absorbed and excreted by the liver, and therefore only one dose per day is required.
Side e ects
Common side e ects include abdominal distension and pain, borborygmi, nausea and vomiting, atulence and diarrhoea. Laxative dependence has not been seen in children. Laxatives should not be used in the presence of intestinal in ammation, perforation or obstruction. Again, laxatives are largely free of drug interactions, although there may be transient reduced absorption of other medications because of increased gut motility.
NICE (2010) recommends treatment that is centred around the use of stimulant and osmotic laxatives, but it is useful to look at all the classes.
Osmotic laxatives
ese exert their action by drawing the water from the body via the digestive tract into the bowel and makes the stool wet. is increases the bulk of the stool as well as so ening it. Increased stool bulk triggers colon motility and passage of the stool. Dehydration can
be a problem and adequate uid intake is important. Electrolyte imbalance is also possible, with sodium and potassium being drawn into the gut with the water.
Macrogol preparations are recommended by
NICE (2010) as the rst line of treatment. Macrogol preparations are a slightly di erent class: iso-osmotic laxatives retain water in the bowel rather than drawing it from the body, so there is no net movement of
water to or from the digestive tract. All formulations available in the UK include added potassium and sodium to minimize the movement of electrolytes across the digestive tract. Movicol Paediatric Plain
is the only licensed preparation that can be used in children under 12 years of age (NICE, 2010). Previous studies have shown that it can be used safely and e ectively in children under 2 years, although it is
not licensed for this age group (Malakounides and Clayden, 2008).
Side-e ects of macrogols are no di erent from those expected. ere is an additional contra- indication against its use in patients with severe in ammatory bowel disease, such as Crohn’s disease.
e most common osmotic laxative in children is lactulose. However, lactulose has been shown to be less e ective than macrogols (Voskeiyl, 2004) and takes at least 48 hours to have an e ect. Its advantage is that it is licensed from 1 month of age. Again,side-e ects are as expected, but because lactulose is
a synthetic sugar and similar in structure to lactose there is the additional contra-indication against use in galactosaemia and it must be used with caution in children with lactose intolerance (because it contains some lactose).
Stimulant laxatives
Stimulant laxatives encourage the colonic nerve endings to increase gut motility, and therefore passage of the stool. However, recent studies suggest they
also alter uid and electrolyte absorption, possibly by stimulating active intestinal ion secretion (American Hospital Formulary Services, 2012). Generally the
stool should be so ened by use of an osmotic laxative or faecal so ener before use of a stimulant laxative (Joint Formulary Committee for Children, 2012). NICE recommends its use as an add-on when macrogols alone are ine ective, or instead of macrogols when theformer is not tolerated. E ect is usually seen within 8–12 hours, and therefore it is usually taken at bedtime to produce an e ect the following morning.
e naturally occurring senna is o en used in children to treat constipation, and before the advent of the macrogols was, with lactulose, the main stay of treatment. It is licensed from 1 month of age.
Other stimulant laxatives used in the management of childhood constipation are bisacodyl, a synthetic compound (licensed from 4 years) and sodium picosulfate (another synthetic compound licensed from 1 month of age).
Side e ects are as expected, particularly abdominal cramps as a result of enhanced colonic contraction.
If used in high doses, stimulant laxatives can cause signi cant diarrhoea, which may result in hypokalaemia (Joint Formulary Committee for Children, 2012).
Senna is contra-indicated in severe in ammatory bowel disease, for example, Crohn’s disease.