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.

THANK YOU