38. Drug treatment and mechanisms of action for GORD/peptic ulcers(?) Flashcards
List the types of drug treatment which may be used for GORD
Antacids Alginates H2 receptor antagonists PPIs Prokinetics Sulcrafate
Describe the mechanism of action of antacids.
(are predominantly aluminium and magnesium salts)
Increase the gastric pH
Decrease pepsin activity
Some bind bile acids
Duration of action depends on rate of gastric emptying
Describe some of the problems caused by antacids
Aluminium salts - can cause constipation
Magnesium salts - can cause diarrhoea
Some formulations have high sodium levels - need to be avoided in cardiac/renal disease
What drugs can antacids interact with?
Digoxin, prednisolone, iron, tetracyclines
What are alginates and their mechanism of action?
Sodium alginate - used for the treatment of GORD
Alginates are a mixture of polyurionic acids
Added to acids as foaming agents
Forms a layer of foam on stomach contents to act as a mechanical barrier to reflux
Name 2 prokinetics and how they are used in the treatment of GORD
Metoclopramide
domperidone
Both increase rate of gastric emptying and increase LOS pressure
Metoclopramide also acts on cholinergic systems in the GI tract to increase ACh release
What makes pro kinetics useful in the treatment of GORD?
Early satiety
belching
Help with nausea and bloating
What are the adverse effects of pro kinetics?
Drowsiness
Diarrhoea
hyperprolactinaemia
What is sulcrafate?
A complex sucrose polymer which is also a cytoprotective agent
Describe the mechanism of action of sulcrafate
anionic sulphate binds to positively charged glycoproteins in ulcer
Forms a paste which impedes the diffusion of acid and acts as a buffer for 6-8 hours
Only 5% absorbed into circulation
Describe the mechanism of action of H2 antagonists
Competitively blocks the H2 receptors on parietal cells
List some of the types of H2 antagonists
Cimetidine
Ranitidine
Famotidine
Nizatidine
What are the side effects of H2 antagonists?
Diarrhoea Dizzinesss, fatigue, rash Derranged LFTs Headaches Cimetidine can cause gynaecomastia & constipation
Define tachyphylaxis
A rapid decrease in response to a drug due to previous long term exposure to that drug
Describe the mechanism of action of PPIs
Accumulate selectively in the acid space of parietal cells
Become activated by undergoing an acid-catalysed rearrangement
This cationic sulfenamide binds irreversibly with sulphydryl groups on the proton pump causing inhibition
Irreversible inhibition leads to longer duration of action compared to H2 antagonists
