Pharmacology for Dentistry

254 Section 7/ Drugs Acting on GIT

STOOL SOFTENER

Docusate acts by its detergent action which
reduces the surface tension.

LIQUID PARAFFIN

It is a petroleum hydrocarbon, an inert
viscous liquid. It is a faecal softener and
causes lubrication of hard scybali by coating
them. Paraffin lubricates the passage of
faeces. It is not absorbed and is safe.

It is indicated in postoperative constipation.
Dose: CREMAFFIN 10-15 ml/day.

Adverse effects include aspiration
pneumonia, perianal pruritus, healing in
perianal region may be delayed, unpleasant
taste, the absorption of fat soluble vitamins
may be affected. Long-term administration
is not recommended.

DOCUSATES

It is an anionic detergent which softens the
stool by water accumulation in intestinal lumen
and emulsifies the colon contents. It is indicated
in obstetric, habitual, geriatric, paediatric
constipation or when straining is to be avoided
(recent myocardial infarction, severe
hypertension, post-operative cases, abdominal
hernia), fissures, haemorrhoids and bed ridden
patients. Dose: 100-200 mg/day.

Side effects include nausea, cramps and
abdominal pain.

STIMULANT LAXATIVES

These drugs exert their laxative action by
increasing motility of colon. They mainly
alter absorptive and secretory activity by
inhibiting Na+ K+ ATPase in mucosal cells,
leading to water and electrolyte accumulation
in lumen. Colicky pain may occur and on the

long term use may lead to hypokalemia.

These drugs are to be avoided in pregnancy

and children. The onset of action occurs in 6-

12 hours after oral administration.

BISACODYL

It is stimulant laxative, when administered

orally or as a rectal suppository it produces

increased peristalsis by direct action on the

mucosa of the colon, usually resulting in a soft,

formed stool.

It is indicated in all forms of

constipation, e.g. in bedridden patients, due

to change of food or environment, illness or

digestive disorders; relief of evacuation in

painful conditions such as haemorrhoids;

pre and postoperatively; pre-paration for

barium enema; preparation of colon for

proctosigmoidoscopy. Dose: DULCOLAX

5-15 mg HS oral and suppository (5-10 mg).

SODIUM PICOSULPHATE

In the colon, sodium picosulphate is

converted in to the active comound bis-(p-

hydroxy diphenyl) pyridyl methane

(BHPM) which stimulates propulsive

activity of the colon, prevents absorption of

water in the colonic lumen and promotes

accumulation of water.

Following oral administration sodium

picosulphate is not absorbed. In colon it is

converted to the active metabolite BHPM,

by the action of arylsulphatases secreted by

the colonic bacteria.

Prolonged use or overdosage can

precipitate the onset of an atonic non-

functioning colon and hypokalemia.

It is indicated in constipation e.g. in

patients with cardiovascular disease, hernia

and anorectal disorders, the elderly and