Gastrointestinal System Flashcards
(45 cards)
Which drug is drug of choice for morning sickness
Doxylamine
Which drug is drug of choice for allergic rhinitis
Steroids
Which drug is drug of choice for urticaria
2nd generation H1 blockers
Which type of drug is drug of choice for peptic ulcer disease
PPI
Which H2 blocker is fast and short acting
Cimetidine
Which H2 receptor antagonist is most potent and long acting
Famotidine
Which drug is drug of choice for post operative aspiration pneumonia
H2 receptor blocker
Which drug is drug of choice for NSAID induced ulcer
PPI
Laxatives modify the fluid dynam- ics of the mucosal cell and may cause fluid accumulation in gut lumen by one or more of following mechanisms:
Inhibiting Na K ATPase of villous cells- impairing electrolyte and water absorption.
(b) Stimulating adenylyl cyclase in crypt cells- increasing water and electrolyte secretion.
(c) Enhancing PG synthesis in mucosa which increases secretion.
(d) Increasing NO synthesis which enhances secretion and inhibits non-propulsive contrac- tions in colon.
(e) Structural injury to the absorbing intestinal mucosal cells.
MOA of dietary fibre (3)
It absorbs water in the intestines, swells, increases water content of faeces-softens it and facilitates colonic transit
Osmotically active products may be formed in the colon by bacterial degrada- tion of pectins, gums, etc. which act to retain water.
Dietary fibre supports bacterial growth in colon which contribute to the faecal mass.
What is the first line approach for simple constipation
Dietary Fibres
Bran feature
bran is useful for prevention of constipation, but not for treating already constipated subjects.
Docusates
It is an anionic detergent, softens the stools by net water accumulation in the lumen by an action on the intestinal mucosa.
It emulsifies the colonic contents and increases penetration of water into the faeces.
Liquid Paraffin feature
Taken for 2-3 days, it softens stools, retards water absorption and is said to lubricate hard scybali by coating them.
Stimulant purgatives
Some of them directly increase gut motility
by acting on myenteric plexus neurones. However,
the more important made of action appears to be
accumulation of water and electrolytes in the gut
lumen by altering absorptive and secretory activity
of the mucosal cell.
●They inhibit Na+
K+
ATPase at
the basolateral membrane of villous cells, thereby
transport of Na+
and accompanying water into
the interstitium is reduced.
●Secretion is enhanced
by activation of cAMP in crypt cells (see Fig.
49.1) as well as
●by increased PG synthesis.
The laxative action of bisacodyl and cascara is
shown to be partly dependent upon increased
●NO synthesis or action in the colon.
Bisacodyl
Administered orally, this synthetic
diphenylmethane purgative is absorbed in the
intestine and excreted in bile to undergo partial enterohepatic circulation.
After activation
in the intestine by deacetylation, it irritates colonic mucosa to increase fluid secretion, as
well as stimulate enteric neurones to promote
peristaltic movements.
Sodium picosulfate
It is hydrolysed by
colonic bacteria to the active form, which then
acts locally to irritate the mucosa and activate
myenteric neurones.
Senna features
Senna is obtained from leaves and pods
of certain Cassia sp., while Cascara sagrada
is the powdered bark of the buck-thorn tree.
Senna MOA
Unabsorbed
in the small intestine, they are passed to the
colon where bacteria liberate the active anthrol
form, which either acts locally or is absorbed
into circulation—excreted in bile to act on
small intestine. Thus, they take 6–8 hours to
produce action.
The active principle stimu-
lates the myenteric plexus to increase peristalsis
and decrease segmentation. They also promote secretion and inhibit salt and water absorption
in the colon.
Castor Oil
This agent is broken down in the small intestine to ricinoleic acid, which is very irritating to the stomach and promptly increases peristalsis.
Prucalopride
It activates prejunctional 5-HT4
receptors on intrinsic enteric neurones (see Fig. 48.2) to
enhance release of the excitatory transmitter ACh, thereby
promoting propulsive contractions in ileum and more
prominently in colon.
Lubiprostone
Lubiprostone is an EP4
receptor agonist which activates
mucosal Cl¯
channels by stimulating guanylyl-cyclase C.
It produces Cl¯
rich intestinal fluid and accelerates colonic
transit. Refractoriness to its beneficial effects in chronic
constipation does not appear to develop even after prolonged use. It also delays gastric emptying.
Inorganic salts as Osmotic Purgatives
Magnesium ions release cholecystokinin which aug- ments motility and secretion, contributing to purgative action of Mag. salts. All inorganic salts used as osmotic (saline) purgatives have similar action-differ only in dose, palatability and risk of systemic toxicity.
Which serotonin receptor agonist (5HT4) is found to have no QT prolongation unlike Cisapride
Prucalopride
