920
P A R T 1 1
Drugs acting on the gastrointestinal system
L
ubricants
Sometimes it is desirable to make defecation easier
without stimulating the movement of the GI tract. This
is done using
lubricants
. People with haemorrhoids and
those who have recently had rectal surgery may need
lubrication of the stool. Some people who could be
harmed by straining might also benefit from this type
of laxative. The type of laxative recommended depends
on the condition of the person, the speed of relief needed
and the possible implication of various adverse effects.
Lubricating laxatives include docusate (
Coloxyl
),
glycerol (generic) and liquid paraffin (
Agarol
).
Therapeutic actions and indications
Docusate has a detergent action on the surface of the
intestinal bolus, increasing the admixture of fat and
water and making a softer stool.
Glycerol is a hyperosmolar laxative that is used in
suppository form to gently evacuate the rectum without
systemic effects higher in the GI tract.
Liquid paraffin is the oldest of these laxatives. It is
not absorbed and forms a slippery coat on the contents
of the intestinal tract. When the intestinal bolus is
coated with liquid paraffin, less water is absorbed out
of the bolus, and the bolus is less likely to become hard
or impacted.
Pharmacokinetics
These drugs are not absorbed systemically and are
excreted in the faeces. Docusate and liquid paraffin are
given orally. Glycerol is available as a rectal suppository.
Contraindications and cautions
These laxatives are contraindicated with allergy to
any component of the drug
to prevent hypersensitivity
reactions
; and in acute abdominal disorders, including
appendicitis, diverticulitis and ulcerative colitis,
when
increased motility could lead to rupture or further
exacerbation of the inflammation.
Laxatives should be
used with caution in heart block, CAD and debilitation,
which could be affected by the decrease in absorption
TABLE 58.1
DRUGS IN FOCUS Laxatives
Drug name
Dosage/route
Usual indications
Chemical stimulants
bisacodyl (Bisalax,
Dulcolax)
10–15 mg PO at night, or one suppository PR
at night
Emptying of the gastrointestinal (GI) tract
before some surgeries or diagnostic
tests (e.g. barium enema); prevention
of constipation and straining after GI
surgery, myocardial infarction (MI),
obstetrical delivery; short-term treatment
of constipation
senna (Senokot)
Two to four tablets PO per day at bedtime or
1–2 teaspoons of granules PO per day at
bedtime
Short-term treatment of constipation;
treatment of encopresis; found in many
over-the-counter (OTC) preparations
Bulk stimulants
lactulose (Actilax,
Chronulac)
15–30 mL PO
Short-term treatment of constipation;
alternative choice for people with
cardiovascular disorders
psyllium (Metamucil)
1 tsp or packet in cold water, one to three
times per day; ½ packet for children
Mild laxative; short-term treatment of
constipation
sodium chloride-sodium
bicarbonate-potassium
chloride solution
(ColonLYTELY )
Dosage: 2–4 L of oral solution on empty
stomach in the evening prior to procedure
Stimulates bowel evacuation prior to
GI examination (e.g. colonoscopy,
sigmoidoscopy)
Lubricants
docusate (Coloxyl,
Sennesoft)
100–240 mg PO
Prophylaxis for people who should not
strain (such as after surgery, myocardial
infarction or obstetrical delivery)
glycerol (generic)
One suppository PR. Allow to remain for
15–30 mins
Short-term treatment of constipation
liquid paraffin (Agarol)
Adults and Paediatric (>6 years): 15–30 mL at
bedtime
Paediatric (3–6 years): 10–15 mL at bedtime
Short-term treatment of constipation
