What Is a Proton Pump Inhibitor? PPIs Explained for UK Patients
Quick Answer
A proton pump inhibitor (PPI) is a medicine that reduces stomach acid by permanently blocking the H+/K+-ATPase enzyme — the proton pump — inside the acid-secreting cells of the stomach lining. PPIs are the most effective treatment available for acid reflux, GORD, peptic ulcers, and H. pylori eradication. Common UK PPIs include omeprazole, lansoprazole, and esomeprazole.
In This Article
What Are Proton Pump Inhibitors?
Proton pump inhibitors — commonly known as PPIs — are among the most widely prescribed medicines in the UK, with tens of millions of prescriptions issued every year. The name refers to what the drug does: it inhibits (blocks) the proton pumps that produce acid in your stomach. The result is a significant, sustained reduction in acid — enough to allow irritated or damaged tissue to heal and to prevent further acid-related injury.
PPIs are not the same as antacids, which you may have taken before. They work in a fundamentally different way, and they are considerably more effective for persistent or frequent acid reflux.
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PPIs vs Antacids vs H2 Blockers: What Is the Difference?
Not all acid-reducing medicines work the same way. Understanding the differences helps explain why your prescriber may have recommended a PPI rather than an over-the-counter remedy.
Antacids (Gaviscon, Rennies, Maalox) neutralise acid already present in the stomach. They work within minutes but last only one to three hours. Suitable for occasional heartburn — not adequate for frequent or persistent GORD.
H2 blockers (famotidine) block histamine receptors in the stomach lining, reducing how much acid the stomach produces. They act faster than PPIs and can be used on demand. Less potent than PPIs overall, but useful for mild to moderate symptoms and nocturnal acid suppression.
Proton pump inhibitors (omeprazole, lansoprazole, esomeprazole) block the final step in acid production — the proton pump itself — irreversibly. A single daily dose suppresses acid for 24 hours or longer. They are the most powerful and longest-lasting option, and the first-line treatment for GORD, peptic ulcers, and H. pylori eradication.
If antacids or H2 blockers have not controlled your symptoms, a PPI is the appropriate next step.
What Conditions Do PPIs Treat?
PPIs are prescribed for a range of conditions where excess or persistent stomach acid plays a role:
- Gastro-oesophageal reflux disease (GORD) — including erosive oesophagitis and Barrett’s oesophagus
- Gastric and duodenal ulcers — reducing acid allows the ulcer to heal
- Helicobacter pylori eradication — PPIs are used alongside antibiotics in combination therapy
- NSAID gastroprotection — co-prescribed to protect the stomach lining in patients on long-term ibuprofen or similar medicines
- Zollinger-Ellison syndrome — a rare condition involving acid-producing tumours
Clinical Note
NICE guidelines recommend that patients at increased risk of gastric complications — including those over 65 taking long-term NSAIDs, or those on anticoagulants or corticosteroids — should routinely receive a PPI.
How Do Proton Pump Inhibitors Work?
To understand how PPIs work, it helps to know how your stomach produces acid.
The cells that line your stomach — called gastric parietal cells — contain a specific enzyme known as H+/K+-ATPase, or the proton pump. This enzyme performs the final step in producing hydrochloric acid. PPIs bind to and permanently disable this pump, preventing acid from being released.
Why the effect lasts longer than the drug
PPIs are prodrugs — they are inactive when you swallow them. After being absorbed into the bloodstream, they travel to the gastric parietal cells and are converted into their active form by the acidic environment inside the cell. In their active form, they irreversibly bind to the proton pump.
Even though the drug itself is cleared from the bloodstream within approximately two hours, the acid-suppressing effect persists for 24 to 48 hours from a single dose. Acid production only resumes once the stomach generates new proton pump molecules — a process that takes around a day. This is why once-daily dosing is sufficient for most people.
PPIs suppress both basal (background) acid secretion and the surge in acid that occurs in response to eating, making them effective throughout the day and night.
Which PPIs Are Available in the UK?
Five PPIs are currently licensed for use in the UK:
| Medicine | Common Brand | OTC Available? |
|---|---|---|
| Omeprazole | Losec | Yes (20 mg) |
| Lansoprazole | Zoton FasTab | Yes (15 mg) |
| Esomeprazole | Nexium | Yes (20 mg) |
| Pantoprazole | Pantoloc | No |
| Rabeprazole | Pariet | No |
Omeprazole and lansoprazole are the most widely prescribed — both are available generically at low cost and have the most extensive evidence base. For most patients, one of these two will be the appropriate first-line choice.
The differences between PPIs — including drug interactions, dosage, when to take them, long-term safety, and which is right for your specific situation — are covered in detail in our complete proton pump inhibitors guide.
Not sure whether you need a PPI or an alternative acid reflux treatment? Our regulated prescribers can review your symptoms and recommend the most appropriate option for you.
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Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting, stopping, or changing any medication. Prescriptions through Access Doctor are issued by GPhC-registered pharmacist independent prescribers following clinical assessment. GPhC registration number 9011198.
Frequently Asked Questions
What is a proton pump inhibitor?
A proton pump inhibitor is a medicine that blocks the H+/K+-ATPase enzyme — the proton pump — inside the acid-secreting cells of the stomach. By permanently disabling this pump, PPIs prevent stomach acid from being produced. The effect lasts 24 to 48 hours from a single dose, making once-daily dosing sufficient for most conditions.
Are proton pump inhibitors the same as antacids?
No. Antacids neutralise acid already present in the stomach and work within minutes, but their effect lasts only one to three hours. PPIs work differently — they block the proton pumps inside gastric cells before acid is produced, providing sustained around-the-clock acid suppression. PPIs are far more effective for frequent or persistent acid reflux.
How long does it take for a PPI to start working?
PPIs do not provide immediate relief in the way antacids do. Most people notice an improvement in symptoms within two to three days of starting a PPI. However, because the acid-suppressing effect builds up with each daily dose, PPIs reach their maximum effectiveness after four to five days of consistent use.
What is the difference between omeprazole and lansoprazole?
Both are PPIs that work through the same mechanism and are clinically equivalent for most conditions. Omeprazole is the most widely studied and is typically the first-line choice. Lansoprazole is often preferred when patients have experienced side effects with omeprazole, or when the omeprazole–clopidogrel drug interaction is a concern. It is also available as an orodispersible tablet for patients who have difficulty swallowing capsules.
Which proton pump inhibitor is available over the counter in the UK?
Three PPIs are available without a prescription from UK pharmacies for short-term use: omeprazole 20 mg, lansoprazole 15 mg, and esomeprazole 20 mg. These are suitable for up to two weeks to treat recognised heartburn symptoms in adults. If you need a PPI for longer than this, or for a condition such as a peptic ulcer or GORD, a prescription is required.
I’ve been prescribed a PPI — how do I take it correctly?
For full guidance on dosage, timing, drug interactions, side effects, long-term safety, and what to do when stopping a PPI, see our complete proton pump inhibitors guide. That guide covers everything you need to know once a PPI has been prescribed.
References
- National Institute for Health and Care Excellence (NICE). Gastro-oesophageal reflux disease and dyspepsia in adults: investigation and management. Clinical guideline CG184. Updated 2023. nice.org.uk/guidance/cg184
- National Institute for Health and Care Excellence (NICE). Scenario: Prescribing a proton pump inhibitor. NICE CKS. 2024. cks.nice.org.uk
- NHS. Omeprazole. NHS medicines information. nhs.uk/medicines/omeprazole
- Medicines and Healthcare products Regulatory Agency (MHRA). Drug Safety Update. gov.uk/drug-safety-update