GI (Pharm)

Question 1

Weak acid secretion

Answer 1

-Ach is released from from vagal fibres in presence of food
-Gastrin, a hormone, from G-cell in antral mucosa is released in presence of food
-Ach binds to muscarinic receptors on parietal cells
-Gastrin binds gastrin receptors on parietal cells
-HCL secreted H out and K in

Question 2

Indirect stronger acid secretion

Answer 2

-Ach and gastrin stimulate release of histamine from paracrine cells
-Histamine stimulate H2 receptor on parietal cell
-This increases CAMP within the parietal cells from breakdown of ATP
-Then K in and H out and increase HCL secretion

Question 3

Cytoprotective layer (mucous epithelium)

Answer 3

-HCo3 secreted neutralizes the acid and creates a mucous gel
-Prostoglandins E2 and I2 synthesized by the mucous-> stimulate mucus, HCO3 and gastric blood flow

Question 4

Alarm features of Dyspepsia

Answer 4

-Vomitting persistent >7 days

-Bleeding anemia, melena

-Abdominal mass or unexplained weight loss 10% of body weight

-Dysphagia -> endoscopy

-Jaundice, family history of gastric/ovarian CA

-Prior ulcer

Question 5

Antacids

Answer 5

-For intermittent mild-moderate episodic heartburn <3 weeks

-Contains a cation+ weak base to neutralize the stomach acid and rises pH

-Increase rate of gastric emptying
-Increase gastrin release

-Stimulates acid release causes acid rebound when antacid wears off

-Acid neutralizing capacity (ANC)

Examples: CaCO3, Al (OH)3, Mg (OH)2

Question 6

Histamine H2 receptor antagonists MOA

Answer 6

-MOA: blocks action of histamine on parietal cells and reduce acid secretion

-Effective nocturnal HCL secretion

-Eg. Famotidine

-Rapid onset and lasts about 10 hours BID dosing

-4-8 Weeks to see response in dyspepsia without H pylori and mild GERD

Question 7

Proton pump inhibitor PPIs MOA

Answer 7

MOA: irreversibly inhibits H/K/ATPase (proton pump) responsible for transporting the H+ out of the parietal cells into the gut of lumen

-Requires 3-4 days of posing to cover all proton pumps

-On empty stomach to increase bioavailability 30-60 min before meals

Question 8

Bismuth subsalicylate MOA

Answer 8

1. Coating and protection, stimulates mucous and bicarbonate secretion
2. Mild antibacterial (H.pylori), prevents diarrhea
3. Binds and neutralizes toxins

-S/E: ASA toxicity and dark stools
-Avoid in patients with bleeding disorders, taking ASA or anticoagulation’s

Question 9

Misoprostol MOA

Answer 9

-Synthetic prostaglandins by increasing mucous and bicarbonate secretion and increasing mucosal blood flow