Proton Pump Inhibitor
A medicine that strongly reduces stomach acid production.
What it means
Proton pump inhibitors block the enzyme that pumps acid into the stomach, reducing acid production far more effectively than antacids or H2 blockers. Omeprazole, lansoprazole and pantoprazole are the common ones.
Used for reflux, peptic ulcers, Helicobacter pylori eradication, and to protect the stomach in people taking NSAIDs.
They work best taken 30 to 60 minutes before food, since the pumps must be active to be blocked — a detail that is frequently not explained and that accounts for some apparent treatment failures.
In practice
Long-term use is associated with reduced absorption of B12, magnesium, calcium and iron, and with a small increase in certain gut infections.
PPIs are among the most commonly continued-without-review medicines in UK practice — started for a short course during an admission and still being taken years later.
Why it matters
Stopping abruptly after long use causes rebound acid over-production and symptoms that feel like the original problem returning. Reducing gradually, or stepping down to on-demand use, works better.
New indigestion in anyone over 55, or indigestion with weight loss, difficulty swallowing, vomiting or anaemia, needs investigation before acid suppression is started. A PPI can mask a cancer while it grows — which is why we will not treat that picture remotely.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026