GI Acid (Akbareli) Flashcards
What is the pH at which dental enamel erodes?
5.5
What is the pH of stomach acid?
2.0
What are some causative agents of ulcers?
- Acid
- Pepsin
- Drugs (NSAIDS)
- H Pylori
What are some defense mechanisms to prevent ulcers?
- Mucus
- Bicarbonate
- Blood flow
- Prostaglandins
What are the two goals of acid prevention?
- Enhance host defense
2. Eliminate causative factors
What 3 types of problems do acid suppression therapy address?
- GERD
- Peptic Ulcers (due to NSAIDS)
- Duodenal and peptic ulcers (due to H Pylori)
Did the incidence of peptic ulcer disease increase or decrease during the 20th century?
Decreased (lower infection rates with H pylori)
Did the incidence of gastroesophageal reflux disease increase or decrease in the 20th century?
Increased (major gastric acid-related disorders)
Who discovered the H2 receptor?
Sir James Black, a scottish pharmacologist
How was the H2 receptor discovered?
By modifying the structure of histamine to Cimetidine
Histamine stimulates contraction of what type of muscle?
Smooth
What blocks histamine?
Mepyramine
What are some actions of histamine?
- Stimulates acid secretion
- Increase HR
- Inhibits contraction of rat uterus 9not blocked by mepyramine)
Where is histamine produced?
Enterochromaffin cells
What stimulates enterochromaffin cells to release histamine?
- Cholecystokinin receptors are stimulated by gastrin (from the endocrine system)
- Muscarinic receptors are stimulated by acetylcholine (vagus X neuronal system) to release histamine
How are gastric parietal cells activated to release gastric acid (three step process)?
- Histamine activates H2 receptors (GPCR)
- cAMP increases
- H/K ATPase pumps activated
What is the main mechanism of action of H2 Receptor Antagonists?
Competitively antagonize H2 receptors on parietal cells by preventing the action of the H/K ATPase pumps
What are three common forms of peptic ulcers?
- Helicobacter pylori-associated
- Non-steroidal anti-inflammatory drug-induced
- Stress-related mucosal damage (SRMD) - critically ill hospitalized patients
What are some lesson common causes of peptic ulcers?
- Zollinger-Ellison syndrome
- Radiation
- Chemotherapy
- Vascular insufficiency
What are 3 ways peptic ulcers may be treated?
- Reduce gastric acid secretion from parietal cells
- Providing a barrier over the lesion itself, or by stimulating endogenous mucopeptide formation
- Eradicating the bacterium Helicobacter pylori
What are some common H2 Receptor Antagonists?
- Cimetidine (Tagamet)
- Ranitidine (Zantac)
- Famotidine (Pepcid)
- Nizatidine (Axid)
What are FDA indications for H2 Receptor Antagonists?
- Treatment of gastric ulcer
- Duodenal ulcer
- Gastroesophageal reflux disease (GERD)
- Pathological hypersecretory conditions (e.g. Zollinger-Ellison Syndrome)
- Heartburn / avid indigestion / sour stomach - OTC
What are 2 unlabeled uses of H2 Receptor Antagonists?
- Part of multi-drug regimen to eradicate Helicobacter pylori in the treatment of peptic ulcer
- Prevention of NSAID-induced gastric damage
How are the H2 receptor antagonists mainly excreted?
In the kidney
Do all the H2 Receptor Antagonists have similar half-lives?
Yes
What is / are the main route(s) of H2 receptor antagonist administration?
- Oral (main)
2. Intravenous (rapid anti-secretory effect for ZE syndrome
What are the adverse effects of H2 receptor antagonists?
Few adverse effects at doses used with current multi-drug therapies used to treat ulcers
How much of the H2 receptor antagonist drugs is metabolized by the liver?
10 to 35 percent
For how many hours are therapeutic levels of H2 receptor antagonist drugs maintained?
Up to 12 hours
Within how many hours do serum concentrations of H2 Receptor Antagonists peak?
1 to 3 hours
Within how many days of H2 receptor antagonists drugs is tolerance developed?
3 days
What occurs upon discontinuation of H2 receptor antagonist drugs?
Rebound response
“Common” Side-effects of H2 Receptor Antagonist Drugs affect what percentage of users?
Less then 3%