A Brief Introduction to Ulcers: What are ulcers, its causes, and symptoms. Classification of Antiulcer drugs and their adverse effects. List of all the screening models available for Antiulcer drugs. Few of the models are explained with their Principle, procedures, Evaluation, and assessment.

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3. Ulcer
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Anti Ulcer Drugs
(a) H2 antihistamines: Cimetidine, Ranitidine,
Famotidine, Roxatidine
(b) Proton pump inhibitors: Omeprazole, Lansoprazole,
Pantoprazole, Rabeprazole,Esomeprazole
(c) Anticholinergics: Pirenzepine, Propantheline, Oxyphenonium
(d) Prostaglandin analogue: Misoprostol
(e) Neutralization of gastric acid (Antacids)
(1) Systemic: Sodium bicarbonate, Sodium citrate
(2) Nonsystemic: Magnesium hydroxide, Mag. trisilicate,
Aluminium hydroxide gel, Calcium carbonate
(f) Ulcer protectives: Sucralfate, Colloidal bismuth subcitrate (CBS)
(g) Anti-H. pylori drugs: Amoxicillin, Clarithromycin, Metronidazole,
Tinidazole,Tetracycline

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Side Effects Of Anti-Ulcer Drugs
• Headache, dizziness, bowel upset, dry mouth, rashes.
• CNS effects like confusional state, restlessness, convulsions and
coma have occurred infrequently in elderly patients
• Diarrhoea/Constipation, Nausea, Loose Stools.
• Abdominal pain, muscle and Joint pain.
• abdominal cramps, uterine bleeding, abortion [Misoprostol]

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Ideal Animal for screening of anti-ulcer drugs
RATS because
• Of continuous secretion of acid.
• Glandular portion of Rat stomach analogous to body of
stomach in man both anatomically and functionally.
• Being omnivorous resembles man nutritionally.
GUINEA pigs are used when Histamine is used to induce Ulcers.

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Screening Methods
• Pylorus Ligation in Rats (SHAY rats)
• Stress Induced Ulcers in Rats
• NSAIDs(Indomethacin) Induced Ulcers in Rats
• Ethanol Induced Mucosal Damage in Rats( Cytoprotective Activity)
• Histamine Induced Gastric Ulcer
• Acetic Acid Induced Gastric Ulcer
• Cysteamine Induced Duodenal Ulcer
• Demaprit Induced Duodenal Ulcer
• Reserpine Induced Chronic Ulcers
• H2-antagonism in isolated rat uterus
• Aspirin Induced Ulcers
• Serotonin Induced Ulcers
• H+ /K+-ATPase (proton pump) inhibition
• Gastric ischemia-reperfusion injury in rats
• Subacute gastric ulcer in rat

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1.Pylorus Ligation in Rats (SHAY rats)
Principle:
The Pylorus part of the stomach was ligated , it causes ulcers
in rats by stopping the passage of gastric contents from stomach and
accumulation of acidic gastric juice in the stomach for longer time.
has been published by Shay et al (1945)
Procedure:
1. Female Wistar rats weighing 150–170/200 g, Starved for 48hours
having access to drinking water ad libitum.
2. Housed singly in cages with raised bottoms of wide wire mesh to
avoid cannibalism and coprophagy.
3. Ten animals are used per dose and as controls. Under ether
anesthesia a midline abdominal incision is made. The pylorus is
ligated. Damage should not occur to the Blood supply or The
Pylorus.
4. The abdominal wall is closed with sutures.

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5. The test compounds are given either orally by gavage or injected
subcutaneously. And placed in Plastic Cylinders closed on both
ends by wire mesh for 19 Hours.
6. The animals are sacrificed in CO2 anesthesia and stomachs are
dissected out.
7. Along the greater curvature the stomach is opened and pinned on
a cork plate. Its inner surface is examined for ulceration with
Stereomicroscope.
8. Contents of the stomach are drained into a graduated centrifuge
tube and acidity is determined by titration with 0.1 N NaOH.
9. The number of ulcers is noted and the severity is recorded with
the following scores:
• 0 = no ulcer
• 1 = superficial ulcers
• 2 = deep ulcers
• 3 = perforation.
ULCER INDEX calculated as
Ulcer index = 10/x
Where x = Total mucosal area/total ulcerated area

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Method 2:
Evaluation of ulcer index UI is calculated:
UI =UN+US+UP×10–1
• UN= average number of ulcers per animal
• US= average of severity score
• UP= percentage of animals with ulcers
Ulcer index of Test Drug compared with control group to detect Anti
Ulcer effect of test Drug.
CRITICAL ASSESSMENT OF THE METHOD
The “Shay-rat” has been proven to be a valuable tool to
evaluate anti-ulcer drugs with various mechanisms of
action.

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2. Stress Induced Ulcers
Principle:
Psychogenic factors, such as stress, play a major role in the
pathogenesis of gastric ulcers in man. The first report of the use of
restraint as stress factor was published by Selye (1936). Hanson and
Brodie (1960) and Bonfils et al. (1966) described methods to study the
effect of anti-ulcer drugs on immobilization stress in rats.
Advantages:
• Technically Simple.
• Do not require anesthesia or surgery.
• Lesions Located in Glandular region of the stomach.
• As Psychogenic factors are involved in the pathogenesis of gastric
ulcers, Psychotropic drugs could be evaluated.

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A. Restraint Induced Ulcers In Rats
Procedure:
1. Wister Albino rats of either sex weighing 150-200 g are housed in separate
cages and divided into groups of 10 for each treatment. The sex ratio of
male to female rats in each group is kept 3-2.
2. Fasted for 36 hours before experiment. Drug is administered orally or
subcutaneously And the animals are put together and tightened the limbs
with adhesive tapes so that they cannot move.
3. Rats are kept under Restraint for 24 hours, then sacrificed and their
stomachs dissected out.
4. Ulcer index and severity are determined

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B. Water Immersion-Induced Restraint Ulcers
Principle:
Cooling of rats in water during the restraint period
accelerates the occurrence of gastric ulcers and shortens the time of
necessary immobilization (Takagi et al. 1964; West 1982)Development
of gastric lesions increases.
Procedure:
• Groups of 8–10 Wistar rats weighing 150–200 g are used.
• After fasting the animals for 24 hours, The test compound is
administered orally.
• Rats are then placed individually in restraint cages vertically, and
then immersed in water bath at 22o C For 16 hours.
• Then the rats are removed from the cages ,dried and Evans blue
(30mg/kg)is injected intravenously via tail vein.
• 10 minutes later they are sacrificed in CO2 Anesthesia, The
stomachs are removed and ligated at both the ends.

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• Formol-saline (2% v/v) is then injected into the totally ligated
stomachs and kept overnight.
• On the next day, the stomach is opened along the greatest curvature,
washed and examined under a 3-fold magnifier for ulcerative lesions.
EVALUATION:
The mean score in control rats is about 25 (range 20–28).
Inhibition of the lesion production is expressed as percentage value.
CRITICAL ASSESSMENT OF THE METHOD:
Like other stress models, the test resembling the psychogenic factor for
ulcer disease in human beings, is used for final drug evaluation only.

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C. Swimming Stress Ulcers
Procedure:
• Albino Rats ; either sex
• Fasted for 24 hours ; free access to water
• Administer the test drugs 30 minutes prior to the stress.
• Rats are forced to swim in deep concrete tube filled with water at
23o C For 5 hours.
• And then the animals are removed and dried .
• Sacrificed and stomach removed ; opened along the greater curvature
and observed for the ulcer lesions.
• The ulcer severity and ulcer index is calculated.

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3.Indomethacin Induced Ulcers in Rats
Principle:
NSAIDs, like indomethacin and acetyl-salicylic acid, induce
gastric lesions in man and in experimental animals by inhibition of cyclo-
oxygenase resulting in less formation of prostacyclin, the predominant
prostaglandin produced in the gastric mucosa.(loss of gastric mucosal
defense) this is an important model for identifying drugs that could be
effective in NSAID induced gastropathy.
Procedure:
• Groups of 8–10 Wistar rats weighing 150–200 g are used.
• The test drugs are administered orally in 0.1% Tween 80 solution 10
min prior to oral indomethacin in a dose of 20 mg/kg (4 mg/ml
dissolved in 0.1% Tween 80 solution)
• Six hours later, the rats are sacrificed in CO2 anesthesia and their
stomachs removed.
• Formol-saline (2% v/v) is then injected into the totally ligated
stomachs for storage overnight.

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• The next day, the stomachs are opened along the greater curvature,
washed and examined under a 3-fold magnifier and observed for the
ulcer lesions.
• Total lesion score (in mm) for each animal measured , The mean count
for each group is calculated.
• Ulcer index and analysis of stomach contents is done.
EVALUATION:
The mean score in control rats is about 25 (range 20–28).
Inhibition of the lesion production is expressed as percentage value.

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4. Ethanol Induced Mucosal Damage in Rats
Principle:
Ethanol damages superficial epithelial layers and inhibits
prostaglandin release. The agents that protects ethanol induced ulcers
might be cytoprotective and exerts its action by stimulating the release of
endogenous prostaglandins and mucin. (Robert et al. 1979; Szabo et al.
1981.)
Procedure:
• Male Wistar rats weighing 250–300 g are fasted 18 h prior to the
experiment ; water ad libitum.
• Rats are given test drugs or standard drugs orally.
• 30 minutes later 1ml/200g of 99.80% alcohol is administered orally.
• After 1 hour, rats are sacrificed and stomachs are dissected out.
• Severity score and ulcer index are calculated.
• Witt et al. (1985) described a method to quantify the extent of ethanol
induced gastric lesions.

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• A Transmission densitometer is used to measure the optical density
of the photographic negatives of gastric mucosa.
• The damaged areas have lower optical density values.
• EVALUATION : The significance of differences in optical density
between control and ethanol treated tissue is evaluated by
nonpaired single tail student’s t-test.
CRITICAL ASSESSMENT OF THE METHOD
• Several prostaglandins provide cytoprotection, particularly in rats,
in a dose-range which has no antisecretory activity.
• However, clinical experience with prostaglandins showed that ulcer
healing is only achieved at antisecretory doses (Lindberg et al.
1990)
• Therefore, itseems very likely that the cytoprotective property of a
compound in rats has very limited relevance to prediction of its
ulcer healing potential in humans if cytoprotection is really
separated from its antisecretory potential (Herling and Weidmann
1994).

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5.Histamine induced gastric ulcer
• Histamine ( H2 Receptor activation),Male guinea pigs of 300-400g are used
• Fasting : 36-48 hours, 50 mg of histamine sulphate is injected via
intraperitoneal route.
• Test drugs are administered after 30-45 mins of histamine injection.
• 5 mg of Promethazine HCl is given before and after histamine injection. And
sacrifice the animals after 4 hours.
• The degree of ulceration , gastric contents ,Total acidity , Free acidity and
Ulcer index are assessed and calculated.
6. Acetic acid induced gastric ulcer
• Overnight fasted rats operated under ether anesthesia , anterior and
posterior walls of stomach clamped with forceps.
• 0.2 ml of 40% acetic acid injected into clamped portion.
• The acid is removed after 45 seconds , deep round ulcers develops on the
anterior and posterior walls.
• Respective treatment ( control, test , standard) started from 3rd day to 10th
day , rats are sacrificed on the 10th day .
• Ulcers respond well to most anti ulcer drugs like Proton pump inhibitors ,H2
Blockers and cytoprotectives.

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7.Cysteamine induced Duodenal Ulcer
• Decreases the mucous production ,increases gastrin and gastric acid
activity, and delayed gastric emptying
• Female sprague-dawley rats weighing 150-200 g are used.
• The test and standards are administered 45 mins prior to the Cysteamine.
a) Oral route : 28mg/100g is administered 3 times at an interval of 3.5
hours and animals are sacrificed after 28 hours of first dose.
b) S.C Route : 20mg/100g administered 2 times at hours interval and
sacrificed after 40 hours of first dose.
• Perforating duodenal ulcers are produced ,located 2-4 mm from the pylorus
mainly on the anterior wall of the duodenum. Severity and ulcer index are
calculated.
8.Dimaprit Induced Duodenal Ulcer
• H2 Receptor agonist , single i.v dose induce gastric erosion in rats and
repeated s.c dose induce duodenal ulcer in guinea pigs.
• Wistar rats(150-200g) guinea pigs(250-300g) are used.fasting:24 hours
,water ad libitum.
• Test or standard are given orally 60 min before dimaprit inj in rats and 30
mins before injecting in guinea pig.
• Dose: 100mg/kg i.v in rats and 2mg/kg s.c in guinea pig (every h for 6h)
• After 1 h , animal sacrificed stomach dissected out examined for
ulceration.

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