Pharmacological basis of therapy Flashcards
Antagonist affinity
Measure of how well a drug binds to a receptor
Prostaglandin analogue
Misoprostol - agonist at PG receptors
Suppress acid release + promote cytoprotection
Cause uterine contractions
Prokinetic drugs
Cause gastric emptying - movement of gastric contents from stomach to duodenum (help GORD)
Example of prokinetic drugs
DOMPERIDONE
METOCLOPRAMIDE
What can metoclopramide be combined with?
Analgesics - to accelerate absorption
How do we eradicate H.pylori?
Triple therapy
What is triple therapy?
Combination therapy
What does triple therapy consist of?
2 antibiotics + PPI and/or H2RA
How long to take triple therapy?
1 week then PPI alone
Example of PPI
Omeprazole
Pantoprazole
Lansoprazole
What PPIs are OTC
Omeprazole + pantoprazole
Adverse effects of PPIs
Inhibit H+ secretion by more than 90% - leading to achlorydria
Increase risk of Campylobacter infection (food poisoning)
Adverse effects of PPIs
Inhibit H+ secretion by more than 90% - leading to achlorydria
Increase risk of Campylobacter infection (food poisoning)
What activates PPIs
Acidic pH
- enters body
- passes to parietal cells
- pka means activated at low pH
- localises action
What is rebound acid hypersecretion
Follows after cessation of H2RAs + PPIs
Increases acid release
Increase dyspepsia symptoms
Avoid prolonged usage
How do you treat/manage rebound acid hypersecretion?
Antacids
Affinity constant
Ka
Dissociation constant
1/Ka = Kd
Kd
Concentration at which the drug occupies half of the receptor population
A high affinity drug has…
A low Kd (low molarity drug)
Examples of H2RA
Cimetidine
Ranitidine
Nizatidine
Famotidine
H2RA
Coupled with adenylyl cyclase to increase cAMP
which activates the proton pump
Alginates
Combine with saliva to form viscous foam
Floats on gastric content forming a raft which protect oesophagus from reflux
Examples of antacids
Sodium bicarbonate
Magnesium hydroxide
Aluminium hydroxide