C H A P T E R 5 8
Drugs affecting gastrointestinal motility
923
ANTIDIARRHOEALS
Antidiarrhoeals
block stimulation of the GI tract for
symptomatic relief from diarrhoea. Available agents
include loperamide (
Imodium
), kaolin, codeine and
opium derivatives. Several antidiarrhoeal products
are available in combination (Box 58.3). Other anti
diarrhoeals are salicylate derivatives that are used
to reduce inflammation and associated diarrhoea in
individuals with inflammatory bowel disease, such as
ulcerative colitis. These include balsalazide (
Colazide
),
mesalazine (
Pentasa, Mesasal, Salofalk
and others) and
olsalazine (
Dipentum
).
There is also a drug approved strictly for use in pre-
venting traveller’s diarrhoea (Box 58.4).
Therapeutic actions and indications
Antidiarrhoeal agents slow the motility of the GI tract
through direct action on the muscles of the GI tract to slow
activity (loperamide) or through action on CNS centres
that cause GI spasm and slowing (opium derivatives; see
Figure 58.1). These drugs are indicated for the relief of
symptoms of acute and chronic diarrhoea, reduction of
volume of discharge from ileostomies and prevention and
treatment of traveller’s diarrhoea (Table 58.2; Box 58.4).
Bovine colostrum (
Travelan
) has been found to be very
helpful in treating traveller’s diarrhoea (
see the Critical
thinking scenario for additional information
).
Pharmacokinetics
Loperamide is slowly absorbed after oral administra-
tion, metabolised in the liver and excreted in urine and
faeces. It may cross the placenta and enter breast milk.
Codeine, a controlled substance, is readily absorbed
after oral administration, metabolised in the liver and
excreted in urine. It crosses the placenta and enters
breast milk.
Salicylates are readily absorbed directly from the
stomach, reaching peak levels within 5 to 30 minutes.
They are metabolised in the liver to salicylic acid, an
active metabolite and excreted in the urine, with a
half-life of 15 minutes to 12 hours, depending on the
salicylate. Salicylates cross the placenta and enter breast
milk; they are not indicated for use during pregnancy or
breastfeeding because of the potential adverse effects on
the neonate and associated bleeding risks for the mother.
Some popular antidiarrhoeal agents combine different
compounds.
codeine, kaolin,
aluminium
hydroxide,
pectin
(
Bis-Pectin
)
Adult and paediatric (>12 years):
15 mL hourly for three doses, then
q 3 hours
Paediatric (8–11 years): 11 mL
q 4 hours
diphenoxylate
with atropine
(
Lofenoxal,
Lomotil
)
Adult: 5 mg PO t.d.s. or q.i.d.
initially, reducing when controlled
■■
BOX 58.3
Combination antidiarrhoeal products
Recently, bovine colostrum (
Travelan
) has been
approved for use in prevention of traveller’s diarrhoea.
The preparation contains high levels of antibodies
against
E. coli
to prevent infections caused by the
bacteria, a common cause of traveller’s diarrhoea.
Other available products work to manage diarrhoea
from
E. coli
infection once it has occurred. One capsule
is taken before each meal, and additional capsules can
be taken if needed in between meals when there may be
increased risk of infection.
■■
BOX 58.4
Treating traveller’s diarrhoea
TABLE 58.2
DRUGS IN FOCUS Antidiarrhoeals
Drug name
Dosage/route
Usual indications
bovine colostrum
(Travelan)
200 mg PO t.d.s. on empty stomach at least
1 hour before food and 2 hours after
Management of traveller’s diarrhoea
loperamide (Imodium)
Adult: 4 mg PO, then 2 mg PO after each loose
stool
Short-term treatment of diarrhoea
associated with dietary problems, viral
infections
Ulcerative colitis drugs
balsalazide (Colazide)
Three 750-mg capsules PO t.d.s. for 8 weeks
Treatment of mildly to moderately acute
ulcerative colitis in adults
mesalazine (Pentasa,
Mesasal, Salofalk,
others)
500 mg PO t.d.s.; one enema at bedtime or
one suppository once daily
Treatment of ulcerative colitis and other
inflammatory bowel disease in adults
olsalazine (Dipentum)
1 g/day PO in two divided doses
Treatment of ulcerative colitis and other
inflammatory bowel disease in adults
