JOVANA
Library Glossary Getting Started Three Levels Fields How it works Mission
Join the mission
All guides

Taming Stomach Acid: Antacids, H2 Blockers and PPIs

Three ways to deal with stomach acid — neutralise it, dial it down a little, or switch off the pump that makes it. We follow the acid from cause to cure and see why each drug fits a different job.

Where the acid comes from

The lining of your stomach holds tiny factories called parietal cells. Each one has a pump in its wall — the proton pump — that pushes hydrogen ions (the H in acid) into the stomach. That acid helps digestion, but when there is too much, or the lining is weak, it burns: this is heartburn, reflux, or a peptic ulcer. Three messengers tell the pump to switch on; histamine is the strongest of them, acting through a receptor on the parietal cell.

Parietal cell — acid switch

  histamine ──► H2 receptor ──┐
  gastrin   ─────────────────┼──► proton pump ──► H+ into stomach (acid)
  ACh       ─────────────────┘

Where each drug acts:
  Antacid ......... mops up H+ already in the stomach (after the pump)
  H2 antagonist ... blocks the histamine signal (turns down the dial)
  PPI ............. blocks the pump itself (switches off the factory)
The acid pathway and the point where each drug class steps in.

Three strategies, three drug classes

Mop it up. An antacid is a base (often a magnesium or aluminium salt) that simply neutralises acid already sitting in the stomach. It does nothing to the pump, so relief comes within minutes but fades within an hour or two. Antacids are perfect for the occasional heartburn after a heavy meal.

Turn down the dial. An H2 antagonist (the "-tidine" drugs) blocks the histamine receptor, so the loudest signal to the pump goes quiet. Acid output drops by more than half for several hours — slower to start than an antacid but far longer-lasting. This is its mechanism of action: occupy the receptor and let nothing else bind there.

Switch off the factory. A proton-pump inhibitor (the "-prazole" drugs) ignores the messengers entirely and disables the pump itself — its true enzyme target. Because it binds the active pumps for good, one daily dose suppresses acid for a day or more. PPIs are the strongest acid-reducers and the mainstay for ulcers and stubborn reflux.

Using them well

  1. Match the drug to the problem: an antacid for occasional, quick relief; an H2 blocker for predictable evening symptoms; a PPI for frequent reflux or a diagnosed ulcer.
  2. Mind the spacing: an antacid is a notorious cause of drug interactions because it binds other tablets in the gut. Separate it from other medicines by about two hours.
  3. Do not stay on a PPI forever by habit. Long courses have their own side effects (such as lower magnesium and reduced vitamin B12 over years), so review whether you still need it.
  4. Treat alarm signs as a reason to see a doctor, not to buy a stronger pill: weight loss, trouble swallowing, vomiting blood or black stools are never "just heartburn".