2012A03 Classify
the drugs which are useful for reducing the volume and acidity of gastric
contents,
giving an outline of the mechanism of effect for each group.
List:
· Intro
· Drugs reducing acidity
· Drugs reducing volume
Intro:
|
Risk factors for aspiration injury |
· ↑Volume · ↑Acid · ↑Particulate matter |
|
Physiology |
|
Acidity:
|
Group |
Drug |
Mechanism of action |
|
PPI |
Omeprazole |
· Irreversibly inhibit H+K+ATPase · Most potent class |
|
H2A |
Ranitidine |
· ↓H2R activity -> ↓Gs GPCR -> ↓cAMP -> ↓parietal cell activity |
|
PGE1 analogue |
Misoprostol |
· Binds PGE2, PGE3 · ↑cAMP, Wnt pathway activation |
|
Particulate antacid |
Mg(OH)4 Al(OH)3 |
· H+ + OH- -> H2O · More potent than non-particulate |
|
Non-particulate antacid |
Sodibic |
· H+ + HCO3- -> H2O + CO2 · Less potent but lower risk pneumonitis if aspirated (cf. particulate) |
|
Antimuscarinic |
Atropine Glycopyrrolate |
· Antagonists at m1 and m3 AChR · ↓IP3 -> ↓ICF [Ca2+] (also ↓DAG) · ↓Gastrin, ↓histamine, ↓parietal cell activity |
Volume only:
|
Class |
Drug |
Mechanism of action |
|
DA2 antagonist prokinetic |
Metoclopramide |
· Peripheral DA2 antagonist and 5HT4 agonist -> ↑gastric motility, ↓pyloric sphincter tone |
|
Macrolide prokinetic |
Erythromycin |
· Motilin receptor agonist -> ↑gastric motility |
|
(Pro-emetic) |
Ipecac |
· Irritate gastric mucosa · Stimulate CTZ |