Gastrointestinal System

Question 1

Which drug is drug of choice for morning sickness

Answer 1

Doxylamine

Question 2

Which drug is drug of choice for allergic rhinitis

Answer 2

Steroids

Question 3

Which drug is drug of choice for urticaria

Answer 3

2nd generation H1 blockers

Question 4

Which type of drug is drug of choice for peptic ulcer disease

Answer 4

PPI

Question 5

Which H2 blocker is fast and short acting

Answer 5

Cimetidine

Question 6

Which H2 receptor antagonist is most potent and long acting

Answer 6

Famotidine

Question 7

Which drug is drug of choice for post operative aspiration pneumonia

Answer 7

H2 receptor blocker

Question 8

Which drug is drug of choice for NSAID induced ulcer

Answer 8

PPI

Question 9

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:

Answer 9

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.

Question 10

MOA of dietary fibre (3)

Answer 10

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.

Question 11

What is the first line approach for simple constipation

Answer 11

Dietary Fibres

Question 12

Bran feature

Answer 12

bran is useful for prevention of constipation, but not for treating already constipated subjects.

Question 13

Docusates

Answer 13

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.

Question 14

Liquid Paraffin feature

Answer 14

Taken for 2-3 days, it softens stools, retards water absorption and is said to lubricate hard scybali by coating them.

Question 15

Stimulant purgatives

Answer 15

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.

Question 16

Bisacodyl

Answer 16

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.

Question 17

Sodium picosulfate

Answer 17

It is hydrolysed by
colonic bacteria to the active form, which then
acts locally to irritate the mucosa and activate
myenteric neurones.

Question 18

Senna features

Answer 18

Senna is obtained from leaves and pods
of certain Cassia sp., while Cascara sagrada
is the powdered bark of the buck-thorn tree.

Question 19

Senna MOA

Answer 19

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.

Question 20

Castor Oil

Answer 20

This agent is broken down in the small intestine to ricinoleic acid, which is very irritating to the stomach and promptly increases peristalsis.

Question 21

Prucalopride

Answer 21

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.

Question 22

Lubiprostone

Answer 22

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.

Question 23

Inorganic salts as Osmotic Purgatives

Answer 23

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.

Question 24

Which serotonin receptor agonist (5HT4) is found to have no QT prolongation unlike Cisapride

Answer 24

Prucalopride

Question 25

Lactulose MOA

Answer 25

Lactulose is a semisynthetic disaccharide sugar that acts as an osmotic laxative. It cannot be hydrolyzed by Gl enzymes. Oral doses reach the colon and are degraded by colonic bacteria into lactic, for- mic, and acetic acids. This increases osmotic pressure, causing fluid accumulation, colon distension, soft stools, and defecation.

Question 26

Lactulose MOA in hepatic encephalopathy

Answer 26

In patients with hepatic encephalopathy, lactulose causes reduction of blood NH, concen- tration by 25-50%. The acidic breakdown products of lactulose lower the pH of stools which is unfavourable to NH, producing bac- teria. Ammonia produced by bacteria in colon is converted to ionized NH salts that are not absorbed. For this purpose 20 g TDS or more

Question 27

Lactitol moa

Answer 27

Lactitol is neither absorbed nor digested in ileum, but gets fermented by colonic bacteria into osmoti- cally active and weakly acidic products. Water content of faeces is increased while its pH is lowered. Thus, it discourages NH, producing colonic bacteria and reduces NH, absorption to be helpful in hepatic encephalopathy.

Question 28

Comparision between lactitol and lactulose

Answer 28

The laxative efficacy of lactitol is comparable to that of lactulose, but its palatability and patient acceptability is claimed to be better.

Question 29

Lubricant Laxatives

Answer 29

Glycerol
Mineral Oil

Question 30

Hyoscine moa

Answer 30

Antiemetic action is exerted probably
by blocking conduction of nerve impulses
across a cholinergic link in the pathway leading
from the vestibular apparatus to the vomiting
centre and has poor efficacy in vomiting of
other etiologies.
most
effective drug for motion sickness.

Question 31

Hyoscine moa

Answer 31

Antiemetic action is exerted probably
by blocking conduction of nerve impulses
across a cholinergic link in the pathway leading
from the vestibular apparatus to the vomiting
centre and has poor efficacy in vomiting of
other etiologies.
most
effective drug for motion sickness.

Question 32

How is cofactor pyridoxine helpful in anti-emetic?

Answer 32

Synthesis of GABA blocks CTZ

Question 33

Metoclorpramide MOA

Answer 33

The central antidopaminergic (D2) action of
metoclopramide on CTZ is clearly responsible
for its antiemetic property.
Metoclopramide blocks D2 receptors and has
an opposite effect—hastening gastric emptying
and enhancing LES tone by augmenting ACh
release. However, clinically this action is sec-
ondary to that exerted through 5HT4
receptors.

Question 34

At high concentrations which drug can block 5-HT3
receptors present on inhibitory
myenteric interneurones and in the NTS/CTZ.
The central anti 5-HT3
action appears to be
significant only when large doses are used to control CINV

Answer 34

Metoclorpramide

Question 35

Cisapride moa

Answer 35

The prokinetic action
is exerted mainly through 5-HT4
agonism which promotes
ACh release from myenteric neurones, aided by weak
5-HT3
antagonism which suppresses inhibitory transmission
in myenteric plexus.
Enteric neuronal activation via 5-HT4
receptor also promotes cAMP-dependent Cl–
secretion in the
colon, increasing water content of stools.

Question 36

Cisapride stimulates the propulsion (motility)-that is, gas- trointestinal smooth muscle motility and decreases the transit time of gastrointestinal contents down the length of the tract. As this action has been seen throughout the alimentary tract (from esophagus to colon), its action has also been called

Answer 36

Pan-prokinetic

Question 37

Itopride moa

Answer 37

It is a dopamine D2 receptor antagonist and an acetylcholine esterase inhibitor. It acceler ates gastric emptying, improves gastric tension and sensitivity, and has an antiemetic action.

Question 38

Why itoprode a safer prokinetic agent than othe prides?

Answer 38

As it is not being metabolized by CYP3A4, the drug interaction-related risk of ventricular arrythmia is not encountered. It is metabolized by flavin mono-oxygenases, and itopride is considered a safer prokinetic agent.

Rarely gynecomastia and galactorrhea are reported. The risk of extrapyramidal effects is reported to be low with itopride.

Question 39

Ondansetron MOA for CINV/RINV

Answer 39

Ondansetron blocks the
depolarizing action of 5-HT exerted through
5-HT3
receptors on vagal afferents in the
g.i.t. as well as in NTS and CTZ. Cytotoxic
drugs/radiation produce nausea and vomiting
by causing cellular damage, which releases
mediators including 5-HT from intestinal
mucosa → activation of vagal afferents in the
gut resulting in transmission of emetogenic
impulses to the NTS and CTZ. Ondansetron
blocks emetogenic impulses mainly at their
peripheral origin in the g.i.t. and at their
central relay. It does not block dopamine
receptors.

Question 40

What ondansetron is unable to do?

Answer 40

It does not block dopamine
receptors. Vomiting induced by apomorphine
or motion sickness is not suppressed.

Question 41

Granisetron

Answer 41

It is 10 times more potent than
ondansetron and probably more effective during
the repeat cycle of chemotherapy.

Question 42

NK1
RECEPTOR ANTAGONISTS

Answer 42

Realizing that activation of neurokinin (NK1
)
receptor in CTZ and NTS by substance P
released due to emetogenic chemotherapy and
other stimuli plays a role in the causation of
vomiting, selective antagonists of this receptor
have been produced,

Question 43

Corticosteroids MOA

Answer 43

The basis
of the effect is not known; appears to be due
to their anti-inflammatory action. They also
serve to reduce certain side effects of the
primary antiemetic.

Corticosteroids enhance efficacy against both
acute and delayed emesis.

Question 44

Macrolides MOA in prokinetics

Answer 44

Motilin agonist, small intestine and not colon which increase GI motility

Question 45

Which D2 receptor anatgomist doesnt crosses BBB so has rare EPS and doesn’t block levodopa theraupetic effect in parkinsonism

Answer 45

Domperidone