screening of antiulcer agent
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Transcript of screening of antiulcer agent
Screening of Anti-ulcer drugs
Presented By, Chetan M. Jain
First Year M.Pharm(Quality Assurance)
Government College of Pharmacy,Amravati.
Stomach
ulcer
“A disruption of the mucosal integrity of the stomach and/or duodenum leading to a local defect or excavation due to active inflammation.”
SCREENING METHODS• Pylorus Ligation in Rats• Stress ulcer Model
o Restraint- induced ulcerso Cold water immersion induced ulcer
• Histamine-induced Gastric Ulcer• NSAIDs-induced gastric lesions
PYLORUS LIGATION IN RATSPrinciple:Pylorus is ligated over a certain period of time
Accumulation of gastric acid causes ulceration
Procedure:Wistar rats weighing 150-200 grams
Fasting : 48 hours ; water ad libitum.
Housed singly in cages with raised bottoms of wide wire mesh to avoid coprophagy.
Under anaesthesia, a one-inch midline abdominal
incision is given below the xiphoid process.
Pylorus is ligated without damaging its blood supply.
Stomach is replaced and abdominal wall closed with
sutures.
Test compounds are given either orally or injected s.c.
About 17-19 hours after pyloric ligation,
rats are sacrificed and stomachs are
dissected out.
Contents of the stomach are drained into a graduated centrifuge tube and subjected to analysis for volume, pH, free and total acidity, mucin, prostaglandin, total carbohydrate:protein ratio etc.
Stomach is opened along the greater curvature, pinned on a cork plate.
Its inner surface is examined for ulceration with a binocular microscope.
The ulcer index is calculated and the Ulcer severity graded.
EVALUATION OF THE TEST
Ulcer severity
0 = No ulcer
1 = Superficial ulcer
2 = Deep ulcer
3 = Perforation
Shay et al. (1945)
Ulcer index (UI) :
UI = (UN + US + UP )× 10-1
UN = Average number of ulcers per animal
US = Average of severity scoresUP = Percentage of animals with ulcers
Shay et al. (1945)
Advantage: Evaluates anti-ulcer drugs with various mechanisms
of action and different doses.
Disadvantage: The ulcers localized in antrum of the stomach
InferenceUlcer index of test drug compared with control group
to detect anti-ulcer effect of test drug.
Other parameters help to infer the mechanism of ulcer protection-
Decrease in volume, free & total acidity: antisecretory action
Rise in pH: acid neutralising actionIncrease in mucin, PGs: cytoprotective effect.
Stress Ulcer Modeli. Restraint- induced ulcers (Hanson and
Brodie ,1960)
Principle: Stress plays a significant role in the pathogenesis
of gastric ulcers.
Procedure:Albino rats weighing 150-200 grams are taken
Fasted for 36 hours before experiment
Drug is administered orally or subcutaneously
30 min later animals are subjected to restraint
For restraint, the rats were placed in a piece of galvanized steel window screen of appropriate size.
Screen was moulded around the animal and held in place with wire staples.
To restrain the rats, the limbs were put together in pair and tightened with adhesive tape.
Rats were kept under restraint for 24 hours Rats were then sacrificed & their stomachs dissected
out.
Ulcer index and ulcer severity were determined.
ii. Cold water immersion induced ulcer (Takagi et al, 1964)
Principle:
Exposure of cold conditions to restrained animals
accelerates the occurrence of gastric
ulcers.
Shortens the immobilization time.Procedure:
Wistar rats weighing 150-200 grams are used.
After fasting the animals for 16 hours,
the test compound is administered
orally
Rats are then placed individually in restraint cages vertically, and then immersed in water upto the xiphoid process, at 22°C for 1 hour.
Then rats are removed from the cages, dried
Evan’s blue (30mg/kg) injected i.v. via the tail vein
10 min later, they are sacrificed
The stomach is removed & ligated at both ends
It is filled with Formol saline & kept overnight
On the next day, the stomach is opened along the greater curvature and examined for ulcerative lesions
Histamine-induced Gastric UlcerPrinciple: Gastric acid secretion is increased when histamine is
administered intraperitoneally.
Procedure:Guinea pig weighing 300-400 grams are taken
Fasted for 36 hours before experiment; water ad libitum
1 ml of histamine acid phosphate (50 mg base) was administered i.p.
Promethazine hydrochloride 5 mg was injected i.p. 15 min before and 15 min after histamine to protect the animals against histamine toxicity.
The standard/test drugs were administered p.o. or s.c. 45 minutes before histamine injection.
4 hours after histamine injection, guinea pigs were sacrificed and stomach dissected out.
The gastric contents were subjected to analysisStomach was opened along the greater curvature,
ulcers were identified.
ULCER SCORING : (Barrett et al, 1955)
Type 0 : No visible ulcersType 1 : 10 or less small ulcers, 1-3 mm in diameterType 2 : 11 or more ulcers, 1-3 mm in diameterType 3 : 1 or more ulcers, 4-6 mm in diameterType 4 : 1 or more ulcers, 7 mm or more in diameterType 5 : Perforation of the gastric wall
Advantages:
Produces 100% gastric ulceration
Increased volume of gastric acid secretion
Marked enhancement of free and total acidity.
Principle: NSAID induced gastric damage ; by blocking COX
enzyme, endogenous prostaglandin production inhibited.
Procedure: Rats fasted for 36 hours before Indomethacin
administration (20 mg/kg, orally)
30 min prior to the administration of the Indomethacin, standard/test drug is administered.
Indomethacin-induced gastric lesions
1 hour after Indomethacin administration, Rats are sacrificed, their stomach dissected out and examined for the number of lesions under the microscope.
Ulcer index and ulcer severity are determined.
References
Shay H, Komarow SA, Fels SS, Meranze D, Gruenstein M,Siplet H (1945) A simple method for the uniform production of gastric ulceration in the rat. Gastroenterol 5:43–61
Brodie D A & Hanson H M. A study of the factors involved in the production of gastric ulcers by the restraint technique. Gastroenterology 38:353-60, 1960.
Takagi K, Kasuya Y, Watanabe K. 1964. Studies on the drugs for peptic ulcers. A realiable method for producing stress ulcer in rats. Chem Pharm Bull 12:465-472.
Pathophysiology by S.L. Bodhankar, N.S. Vyawahare, Nirali Prakashan, 6.1 to 6.6.
Principle of Pharmacology by K.D Tripathi.
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