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1.6
Laxatives
1.6.1 Bulk-forming laxatives
1.6.2 Stimulant laxatives
1.6.3 Faecal softeners
1.6.4 Osmotic laxatives
1.6.5 Bowel cleansing preparations
1.6.6 Peripheral opioid-receptor
antagonists
1.6.7 5HT
4
-receptor agonists
Before prescribing laxatives it is important
to be sure
that the patient
is
constipated and that the constipation
is
not
secondary to an underlying undiagnosed com-
plaint.
It is also important for those who complain of constipa-
tion to understand that bowel
habit can vary consider-
ably in frequency without
doing harm.
Some people
tend to consider themselves constipated if they do not
have a bowel movement each day. A useful definition of
constipation is the passage of hard stools less frequently
than the patient’s own normal
pattern and this can be
explained to the patient.
Misconceptions about bowel
habits have led to exces-
sive laxative use.
Abuse may lead to hypokalaemia.
Thus,
laxatives
should generally be avoided except
where straining will
exacerbate a condition (such as
angina)
or
increase the risk of
rectal
bleeding as in
haemorrhoids.
Laxatives
are also of
value in
drug-
induced constipation
,
for
the expulsion of
parasites
after anthelmintic treatment, and to clear the alimentary
tract before
surgery and radiological
procedures
.
Pro-
longed treatment
of
constipation is sometimes neces-
sary.
For
the role of
laxatives in the treatment
of
irritable
bowel syndrome, see p.
61. For the prevention of opioid-
induced constipation in palliative care,
see p.
22.
Children
Laxatives should be prescribed by a health-
care professional
experienced in the management
of
constipation in children.
Delays of greater than 3 days
between stools may increase the likelihood of
pain on
passing hard stools leading to anal
fissure,
anal
spasm
and eventually to a learned response to avoid defaeca-
tion.
In
infants
,
increased intake of
fluids,
particularly fruit
juice containing sorbitol (e.g. prune, pear, or apple), may
be sufficient to soften the stool. In infants under 1 year
of age with mild constipation,
lactulose (section 1.6.4)
can be used to soften the stool;
either an oral
prepara-
tion containing macrogols or,
rarely,
glycerol supposi-
tories can be used to clear faecal impaction. The infant
should be referred to a hospital
paediatric specialist if
these measures fail.
The diet
of
children over
1 year
of
age
should be
reviewed to ensure that it includes an adequate intake
of
fibre
and fluid.
An osmotic
laxative
containing
macrogols (section 1.6.4) can also be used, particularly
in children with chronic constipation;
lactulose is an
alternative in children who cannot tolerate a macrogol.
If there is an inadequate response to the osmotic laxa-
tive,
a stimulant laxative (section 1.6.2) can be added.
Treatment
of
faecal
impaction may initially increase
symptoms of
soiling and abdominal
pain.
In children
over 1 year of
age with faecal
impaction,
an oral
pre-
paration containing macrogols (section 1.6.4) is used to
clear
faecal
mass and to establish and maintain soft
well-formed stools. If disimpaction does not occur after
2 weeks,
a stimulant
laxative (section 1.6.2)
can be
added.
If
the impacted mass is not expelled following
treatment
with macrogols and a stimulant
laxative,
a
sodium citrate enema can be administered.
Although
rectal
administration of
laxatives may be effective,
this
route is frequently distressing for the child and may lead
to persistence of withholding. A phosphate enema may
be administered under specialist
supervision if
disim-
paction does not occur after a sodium citrate enema; a
bowel cleansing preparation (section 1.6.5) is an alter-
native.
Manual
evacuation under
anaesthetic may be
necessary if disimpaction does not occur after oral and
rectal treatment,
or if the child is afraid.
Long-term regular use of laxatives is essential to main-
tain well-formed stools and prevent recurrence of faecal
impaction;
intermittent use may provoke relapses.
For
children with chronic constipation,
it
may be
necessary to exceed the licensed doses of
some
laxatives.
Parents and carers of
children should be
advised to adjust
the dose of
laxative in order to
establish a regular pattern of
bowel
movements in
which stools are soft, well-formed, and passed with-
out discomfort.
Laxatives
should be administered at
a time that
produces an effect
that
is likely to fit
in with the
child’s toilet routine.
Pregnancy
If
dietary and lifestyle changes
fail
to
control
constipation in pregnancy,
moderate doses of
poorly absorbed laxatives may be used. A bulk-forming
laxative should be tried first.
An osmotic laxative,
such
as lactulose,
can also be used.
Bisacodyl or senna may
be suitable,
if a stimulant effect is necessary.
The laxatives that follow have been divided into 5
main groups (sections 1.6.1–1.6.5). This simple clas-
sification disguises the fact that some laxatives have
a complex action.
1.6.1
Bulk-forming laxatives
Bulk-forming laxatives relieve constipation by increas-
ing faecal
mass which stimulates peristalsis;
patients
should be advised that
the full
effect
may take some
days to develop.
Bulk-forming laxatives are of
particular value in those
with small hard stools, but should not be required unless
fibre cannot be increased in the diet.
A balanced diet,
including adequate fluid intake and fibre is of
value in
preventing constipation.
Bulk-forming laxatives are useful in the management of
patients with
colostomy
,
ileostomy
,
haemorrhoids
,
anal
fissure
,
chronic diarrhoea associated with diverticular
disease
,
irritable bowel
syndrome
,
and as adjuncts in
ulcerative colitis
(section 1.5).
Adequate fluid intake
must
be maintained to avoid intestinal
obstruction.
Unprocessed wheat
bran,
taken with food or
fruit
juice,
is
a
most
effective bulk-forming preparation.
BNF 61
1.6 Laxatives
67
1
Gastro-intestinal system