Antacids, H2 antagonists & PPIs.

Chapter 1

Proton Pump Inhibitors

Pharmacology


Review this image again, and it would clearly show you how proton-pump inhibitors work. It does what it says on the box-the drug inhibits H⁺/K⁺ ATPase (proton pump), the final step in the acid secretory pathway. This irreversible inhibition has an effect which is greater, and longer than compared to H₂ antagonists. Although it has a half life of about 1 hour, it accumulates in the canaliculi of the parietal cell, and can affect acid secretion for 2-3 days.


Example of drugs which fall under this category include:


Omeprazole

Lansoprazole

Esomeprazole

Rabeprazole

Pantoprazole

Mutliple Choice Question

Indication


Treatment of peptic ulcer disease should include eradication ofH. pylori.This is because 90% of people who develop ulcers, are found to haveH. pyloriinfection in their antrum.


Current regime for eradication is the 'triple therapy' for 1-2 weeks. Which drug is NOT included in the triple therapy regime?

Scanning electron micrograph (SEM) of colony of Helicobacter pylori.


Image: Wellcome Images

Adverse Effects and Interactions


The PPIs are generally well tolerated. Gastrointestinal disturbances (eg. nausea, vomiting) and headaches have been reported. Rebound acid hypersecretion and dyspepsia may occur after stopping long term treatment of PPIs.


Omeprazole and Lansoprazole inhibit cytochrome P450. We have discussed the effects of this action in the last page. It is also worth remembering that omeprazole reduces the antiplatelet affect of clopidogrel. Weigh this information carefully when prescribing.