GI drugs Flashcards
What are antacids, name some examples, side effects
- Antacids are weak bases which neutralise stomach acid e.g.Mg(OH)2
- Provide immediate relief
- E.g. rennie
- SE: Usually harmless, Mg can cause diarrhoea, Al constipation
What are alginates, some examples and side effects
- Alginates usually also contain antacids
- They form a neutralising raft over stomach acid to prevent reflux
- Provide immediate relief
- E.g. gaviscon
- SE:
Histamine H2 antagonist: how they work, side effects and examples
- They reduce stomach acid product
- They block H2 receptors in parietal cells within the stomach lining
- Examples are cimetidine, ranitidine, famotidine
- Available OTC
- SE: Diarrhoea, dizziness, muscle pain
What is the natural agonist for the H2-receptor?
The local hormone histamine stimulates the release of gastric acid by interacting with a specific type of histamine receptor called the H2-receptor.
PPI: how they work, examples and side effects
- More potent and longer lasting (24hrs+) than H2A
- They also reduce stomach acid production
- Parietal cells in the stomach lining contain the enzyme H+/K+ ATPase (proton pump) - this usually transports H+ into the stomach in exchange for K+
- E.g. omeprazole, lansoprazole, pantoprazole, rabeprazole
- SE: Diarrhoea, dizziness, muscle pain
What is a prodrug
A Prodrug is a molecule that is inactive in itself, and is converted to the active drug in the body, often by an enzymatic reaction, or change in pH of the environment.
The PPIs are activated when they reach the acidic canaliculi of parietal cells.
How has omeprazole undergone chiral switching
There is no difference between the 2 enantiomers of omeprazole as far as the mechanism of action is concerned, but it is possible to use double the dose levels of esomeprazole compared to omeprazole, resulting in greater activity.
