Acid Suppression

Property Non-Particulate Antacids Particulate Antacids Proton Pump Inhibitors H2 receptor antagonists
Example Sodium citrate Aluminium Hydroxide/Calcium carbonate Omeprazole Ranitidine
Uses Aspiration prophylaxis Aspiration prophylaxis Aspiration prophylaxis, GORD, peptic ulceration Aspiration prophylaxis, GORD, peptic ulceration
Absorption Rapid absorption due to high water solubility Lower water solubility results in slower absorption and onset but no risk of alkalosis Absorbed in small bowel, high PO bioavailability 50% PO bioavailability
Distribution Low VD of 0.3 L.kg-1 15% protein bound
Metabolism Prodrug, activated within parietal cell. CYP450 metabolised, inhibits CYP2C19 (reducing, among other things, the antiplatelet effect of clopidogrel) Partial hepatic by CYP450
Elimination Renal of metabolites and active drug Renal of metabolites and active drug
Mechanism of Action Base reacts with gastric acid to produce salt and water Base reacts with gastric acid to produce salt and water Irreversible antagonism of the parietal H+/K+ ATPase Competitive antagonism of the (Gs) H2 receptor, which ↓ cAMP production, ↓ intracellular Ca2+, and ↓ activity of the H+/K+ ATPase
Resp Lower risk of pneumonitis if aspirated Greater risk of pneumonitis if aspirated Potentially increased severity of pneumonia if aspiration occurs (risk with microaspiration in long-term intubated patients) Pneumonitis/pneumonia as per PPI
CVS HR, ↓ BP, and arrhythmogenic with rapid IV administration
Renal Potential metabolic alkalosis No risk of alkalosis Interstitial nephritis
GIT ↑ Gastric pH ↑ Gastric pH ↑ Gastric pH (pH ↑ by ~1), ↓ volume of secretions
Other Taste bad

References

  1. Petkov V. Essential Pharmacology For The ANZCA Primary Examination. Vesselin Petkov. 2012.
  2. ANZCA Feb/April 2012
  3. Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. Oxford University Press. 4th Ed. 2011.
Last updated 2017-08-08

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