What Is a Proton Pump Inhibitor? Uses, Side Effects & How They Work

What Are Proton Pump Inhibitors?

Proton pump inhibitors — commonly known as PPIs — are among the most widely prescribed medicines in the UK. They work by significantly reducing the amount of acid your stomach produces, helping to relieve symptoms caused by excess acid and allowing damaged tissue to heal.

If you have been prescribed a PPI, or you have seen omeprazole or lansoprazole on a pharmacy shelf, you may be wondering exactly how these medicines work, how safe they are, and how long you can take them. This guide covers everything you need to know.

What Are Proton Pump Inhibitors Used For?

PPIs are prescribed for a range of conditions that are caused or worsened by excess stomach acid. They are one of the most effective treatments available for managing these problems and are used by millions of people across the UK every year.

Conditions commonly treated with PPIs

• Gastro-oesophageal reflux disease (GORD), including Barrett’s oesophagus
• Stomach (gastric) ulcers and duodenal ulcers
• Eradication of Helicobacter pylori infection (as part of combination therapy)
• Zollinger-Ellison syndrome, a rare condition caused by acid-producing tumours
• Protecting the stomach lining when taking NSAIDs long-term

Non-steroidal anti-inflammatory drugs (NSAIDs) — such as ibuprofen or naproxen — are a common cause of stomach irritation. When these medicines are needed for more than a few days, a prescriber may recommend a PPI alongside them to protect the gastric lining.

How Do Proton Pump Inhibitors Work?

To understand how PPIs work, it helps to know a little about 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 is responsible for the final step in producing hydrochloric acid. PPIs bind to and block this pump, preventing acid from being released into the stomach.

Why the effect lasts longer than the drug

PPIs are what pharmacologists call pro-drugs. They are inactive when you swallow them, but once they reach the gastric parietal cells — an acidic environment — they are converted into their active form and irreversibly bind to the proton pump.

Even though the drug itself is cleared from the bloodstream within roughly two hours, the acid-suppressing effect persists for 24 to 48 hours. Acid secretion only resumes once the body produces new proton pump molecules, which is why a single daily dose is usually sufficient.

PPIs inhibit both fasting (basal) acid secretion and the acid released in response to eating, making them effective throughout the day and night.

Types of PPI: Omeprazole vs Lansoprazole

Several PPI medicines are available in the UK. The most commonly used are omeprazole and lansoprazole, both of which are available on prescription and — for short-term use — over the counter in pharmacies.

Omeprazole has been shown to produce slightly greater overall acid suppression than lansoprazole, though in clinical practice the difference is rarely significant. Your prescriber will choose the most appropriate PPI based on your medical history, any other medicines you take, and whether you have specific conditions such as liver problems. For a detailed comparison, read our guide to omeprazole, lansoprazole, and esomeprazole compared.

How to Take a Proton Pump Inhibitor

Taking your PPI correctly makes a real difference to how well it works. Follow these guidelines unless your prescriber has given you different advice:

• Take your capsule or tablet in the morning, on an empty stomach — ideally 30 minutes before breakfast
• Swallow capsules whole with a glass of water; do not crush or chew them
• Do not exceed the dose prescribed or recommended by a healthcare professional
• Continue taking the medicine for the full course, even if symptoms improve quickly
• If you miss a dose, take it as soon as you remember — unless it is almost time for the next dose

Side Effects and Safety

PPIs are generally well tolerated, particularly when used for short periods. All medicines can cause side effects, however, and it is important to be aware of them.

Common short-term side effects

• Headache
• Diarrhoea or constipation
• Nausea or stomach pain
• Skin rash

These effects are usually mild and tend to resolve on their own. If they persist or become troublesome, speak to a pharmacist or prescriber.

Rare but serious reactions

PPIs are fully licensed and regulated by the MHRA (Medicines and Healthcare products Regulatory Agency) for use in the UK, and their safety profile has been extensively studied over decades of clinical use.

Long-Term Use and Risks

If you purchase a PPI over the counter, the MHRA recommends limiting use to around two weeks for heartburn or acid reflux. For longer or ongoing use, a prescription from a qualified prescriber is required.

Long-term PPI use — generally defined as use exceeding eight weeks, and particularly use of one year or more — is associated with a number of potential risks that are worth understanding.

Potential long-term risks

• Reduced absorption of vitamin B12, magnesium, calcium, and iron
• Increased risk of hip, wrist, and spinal fractures — especially in those with osteoporosis
• Higher risk of gastrointestinal infections, including Clostridium difficile
• Increased susceptibility to Helicobacter pylori infection
• Potential increased risk of kidney disease with very prolonged use
• Greater frequency of certain respiratory infections, including pneumonia

These risks are most relevant to people taking PPIs continuously for over a year. If you have been taking a PPI long-term, it is worth reviewing this with a prescriber to ensure you still need it — and, if so, at the lowest effective dose.

PPIs are contraindicated in people with significant liver failure and in anyone with a known allergy to any proton pump inhibitor. If you have a history of liver problems, always inform your prescriber before starting a PPI.

PPIs During Pregnancy

Heartburn is extremely common during pregnancy, and many women require treatment. Of the available PPIs, omeprazole has the most clinical evidence for use in pregnancy and is not known to be harmful to the developing baby when used as directed.

Other PPIs — including lansoprazole, esomeprazole, and pantoprazole — do not have the same level of evidence and are generally not recommended during pregnancy. If you are pregnant or trying to conceive, always discuss your acid reflux treatment with a qualified prescriber before making any changes.

When to Seek Urgent Help

Similarly, if your acid reflux or heartburn does not improve after two weeks of over-the-counter PPI use, you should consult a healthcare professional rather than continuing treatment without guidance.

Treat Acid Reflux Safely Online

Access Doctor offers regulated online consultations for acid reflux and GORD. Our qualified pharmacist independent prescribers can assess your symptoms and prescribe appropriate treatment, including PPIs where clinically indicated.