Module 9: Gastrointestinal Drugs

Question 1

Gastrointestinal Drug classes

Answer 1

• Anti-ulcer drugs
• Adsorbent, anti-flatulent, digestive drugs
• Obesity drugs
• Anti-diarrheal, laxitive drugs
• Anti-emetic, emetic drugs

Question 2

G.D.

Anti-ulcer drugs

Classes:

Answer 2

• Eradicae H. pylori, restore balance between acid and pepsin secretions and GI mucosal defense
• Systemic antibiotics, antacids, H2-receptor antagonists, proton pump inhibitors, other anti-ulcer drugs

Question 3

Peptic ulcer causes

Answer 3

• Bacterial Infection: Helicobacter pylori (gram negative bacterium)
• use of non-steroidal anti-inflammatory drugs (NSAIDs)
• Hypersecretory statae (excess gastric acid)
• Cigarette smoking: causes hypersecretion, impairs ulcer healing
• Genetic predisposition: 20-50% of peptic ulcers

Question 4

Anti-Ulcer drugs

Systemic Antibiotics:

-Dairy products:

Adverse effects:

Answer 4

• Treat H. pylori infection [amoxicillin, clarithromycin, metronidazole, tetracycline]
• decrease absorption [especially tetracycline]
• GI disturbances

Question 5

Anti-Ulcer drugs

Antacids:

Adverse Effects:

Answer 5

-primarily used to relieve pain [aluminum hydroxide, calcium carbonate, magnesium hydroxide, sodium bicarbonate]

• Over-the-counter (OTC) medications
• Neutralizes stomach gastric acid, allowing ulcers to heal

-diarrhea, constipation, electrolyte imbalances, aluminum accumulation in serum.

Question 6

Anti-Ulcer drugs

H2-receptor Antagonists:

Cimetidine:

Adverse Effects:

Answer 6

• Block histamine from stimulating acid-secreting parietal cells of stomach [cimetidine, famotidine, nizatidine, ranitidine]
• acid secretion in stomach depends on binding of gastrin, acetylcholine, histamine to receptors on parietal cells; bind one of these substances and acid secretion reduced
• inhibits metabolism of alcohol in stomach➡ higher blood alcohol levels
• altered hepatic, renal function

Question 7

How H2-receptor Antagonists work

Answer 7

Histamine binds H2 receptor on parietal cell➡ ATP converted to cAMP➡ hydrochloric acid (gastric acid) secreted➡ ulcer results

H2-receptor antagonist competitively binds H2 receptor on parietal cell➡ histamine pathway to gastric acid secretion inhibited.

Question 8

Anti-Ulcer drugs

Proton Pump Inhibitors:

Adverse Effects:

Answer 8

• Disrupt chemical binding in stomach cells to reduce acid production [esomeprazole, lansoprazole, omeprazole]
• Highly unstable in acid, given orally in enteric-coated formulas to bypass stomach; absorbed from small intestine
• Combine with hydrogen, potassium, adenosine triphosphate in parietal cells of stomach to block gastric acid secretion.
• Adverse effects: abdominal pain, diarrhea, nausea, vomiting

Question 9

Other Anti-ulcer Drugs

• Misoprostol:
• Sucralfate:

Answer 9

• for peptic ulcers caused by NSAIDs; reduces gastric acid secretion, increases gastric mucus production
• reacts with hydrochloric acid to form paste that adheres to gastric mucosa, especially ulcers, protecting it from damaging effects of acid, pepsin

Question 10

G.D.

Absorbents, Anti-flatulents, Digestives

Classes
-Absorbents:

• Anti-flatulents:
• Digestives:

Answer 10

• Used to fight undesirable toxins, acids, gases in GI tract; aid healthy GI function
• antidotes for poison overdose [activated charcoal]
• produce film in GI tract that disperses mucus-enclosed gas pockets; are not absorbed [simethicone]
• aid digestion [pancreatin, lipase, protease, amylase]

Question 11

G.D.

Obesity Drugs:

Classes

• appetite suppressants:
• Fat blockers:

Adverse effects:

Answer 11

• For morbidly obese with health probems that improve with weight loss or prevent death. Not meant for cosmetic weight loss.
• increase norepinephrine/dopamine in brain➡ appetite suppressed [phentermine, sibutramine]
• blind lipases; ~30% of fat not broken down➡ decreased fat absorption/fat soluble vitamin absorption [orlistat]
• dry mouth, constipation, hypertension, fatty stools.

Question 12

Anti-diarrheal Drugs

Classes:

• Opioid-related:
• Kaolin and pectin:
• 5-HT3 receptor antagonists:

Adverse Effects:

• Opioid-related drugs:
• Kaolin and pectin:
• 5-HT3 receptor antagonists [alostron]:

Answer 12

• For relief of diarrhea
• slow GI motility by depressing perstalsis in large/small intestines [diphenoxylate with atropine, loperamide]
• absorb irritants (bacteria, toxins); soothe intestinal mucosa by decreasing pH
• block serotonin in GI system to reduce cramping, urgency, diarrhea of IBS [alosetron: restricted access, serious adverse effects]
• nausea, vomiting, abdominal discomfort, drowsiness, fatigue, CNS depression, tachycardia, paralytic ileus (reduced/absent intestinal perstalsis)
• constipation in elderly
• ischemic colitis, constipation, obstruction, perforation, toxic megacolon.

Question 13

Laxitive Drugs

Classes:
-Hyperosmolars:

• Dietary fiber:
• Emollients:
• Stimulants:

Lubricants:

Adverse Effects

• Hyperosmolars:
• Dietary Fiber:
• Emollients:
• Stimulants:
• Lubricants:

Answer 13

-For relief of constipation

• draw water into intestines, promoting bowel distention/peristalsis [glycerin, lactulose, magnesium salts, sodium biphosphate, electrolytes]
• bulk-forming, non-digestible plant fiver; intestinal bacteria covert into osmotically active metabolites that draw water into intestines; natural treatment [methylcellulose, psyllium]
• promote perstalsis by irritating intestinal mucosa [castor oil, bisacodyl, cascara sagrada, senna]
• prevent water reabsorption [mineral oil]
• fluid, electrolyte imbalances
• gas
• seldom any
• abdominal cramping
• diarrhea

Question 14

Anti-emetic drugs:

-Adverse Effects:

Emetic drugs:

Answer 14

• decrease nausea, reducing urge to vomit; various mechanisms (affect vomiting center in brain or vagal nerve terminals) [ondansetron, scopalamine, metoclopramide, dronabinol]
• paradoxical CNS stimulation, confusion, anxiety, dry mouth, orthostatic hypotension, increased heart rate.
• induce vomiting in poisoning, drug overdose; stimulates brain vomiting center [ipecac syrup]; adverse effect are rare.