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

 

 

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