PPIs Flashcards
what does the stomach secrete?
HCL/ bicarbonate/ pepsinogen/ intrinsic factor/ mucus / prostaglandins/
what is the role of the intrinsic factor?
a glycoprotein that facilitates gastric absorption of vitamin B12
how is the stomach divided?
Stomach is divided into three functional areas, each with specific glands
cardiac/ pyloric and gastric area
what is the role of the different areas in the stomach?
- Cardiac–the uppermost area of the stomach by the cardiac sphincter, contains cardiac glands
- Pyloric–pyloric zone is lowermost part of the stomach, contains the pyloric glands
- Gastric–fundus is the larger part of the body of the stomach, contains gastric glands–gastric glands play the most significant role in acid-related disorders–cells of gastric gland are the largest in number and of primary importance in acid control
what do different cells regulate in the stomach?
•parietal … gastric acid, intrinsic factor
chief … pepsinogen
•mucoid… mucus
what is the role of the parietal cell in the gastric gland?
- Produce and secrete HCl
* Primary site of action for many acid-controller drugs
what does HCL do in the gastric gland?
•Secreted by the parietal cells –stimulated by food –Large fatty meals –Excessive amounts of alcohol –Emotional stress •Maintains stomach at pH of 1 to 4
how is HCL regulated in the stomach?
The proton pump H+/K+ATPase
•Pumps protons out of the parietal cell and potassium ions back in
Potassium ions exit the parietal cell as counterionsfor the chloride ions and are then pumped back in
where is HCL formed?
canaliculus
what role do the chief cells have in the gastric gland?
–Secrete pepsinogen, a proenzyme
–Pepsinogen becomes pepsinwhen activated by exposure to acid
–Pepsin breaks down proteins (proteolytic)
what role do mucoid cells have in the gastric gland?
–Mucus-secreting cells (surface epithelial cells)
–Provide a protective mucous coat
–Protect against self-digestion by HCl
what happens if there is an imbalance of the 3 cells of the gastric gland and their secretions?
Hyperacidity–most common
–overproduction of HCl by the parietal cells
/ PUD/
h. pylori–Bacterium found in GI tract of 90% of patients with duodenal ulcers, and 70% of those with gastric ulcers
/ GURD
what are some acid controlling agents?
antacids
H2antagonists
PPI
what are some examples of antacids?
- any (non-corrosive) alkali could be used
- sodium (or potassium) bicarbonate
- calcium (or magnesium) carbonate
- aluminium hydroxide, magnesium trisilicate
- may include other agents to help alleviate condition; for example, alginates
give some examples of h2 receptor antagonists?
•cimetidine •famotidine •ranitidine
what are some examples of PPIs?
•lansoprazole •(es)omeprazole •rabeprazole •pantoprazole
what are Antacids MOA?
- Antacids DO NOT prevent the over-production of acid
- Antacids DO neutralize the acid once it’s in the stomach
- Quick onset of relief but last for a short duration
- Simple acid-base reaction
- Promote gastric mucosal defense mechanisms
- Reduction of pain associated with acid-related disorders
what effect does raising the ph from 1.3-1.6 have?
neutralizes 50% of the gastric acid
what effect does rasising the ph to 1.3 to 2.3 have?
neutralizes 90% of the gastric acid
what is an alginate?
- Polysaccharides derived from seaweeds–Usually used as sodium salt
- Alginates gel in solution due to cross-linking
- Especially good in the presence of calcium ions
how do alginates work?
- Produces a ‘raft’
- Bicarbonate produces CO2gas and floats raft
- Prevents reflux
what do h2 antagonists do?
reduce acid secretion
•Block histamine (H2) at the receptors of acid-producing parietal cells–production of hydrogen ions is reduced, resulting in decreased secretion from the parietal cells
what happens when histamine is blocked?
Up to 90% inhibition of vagal and gastrin stimulatedn acid secretion occurs when histamine is blocked
results in increase in ph in the stomach
what is a PPI moa?
–irreversibly bind to H+/K+ATPase
enzyme–result: achlorhydria
•gastric acid secretion is blocked