H2 Blockers

H2 blockers are drugs that reduce the amount of acid the stomach makes. They can be used to treat reflux, heartburn and some stomach and duodenal ulcers.

These drugs are not steroids (cortisone) or antibiotics. They are not addictive.

How do H2 blockers work?

The stomach makes acid to help digest food. However, stomach acid escaping into the gullet can cause burning, and damage to the protective layer of the stomach and duodenum can cause ulcers.

One of the substances that increases acid production in the stomach is histamine. H2 blockers block the effect of histamine on the stomach cells and so reduce acid production.

In this way, complaints such as heartburn and acid indigestion can ease.

Which drugs are H2 blockers?

The main active ingredients in this group are:

• Famotidine: One of the H2 blockers in use today.
• Cimetidine: Reduces stomach acid, but its use is limited because it interacts more with other medicines.
• Nizatidine: In the same group; its availability varies from country to country.
• Ranitidine: Was widely used in the past. However, because an unwanted substance called NDMA was found in some products, it was withdrawn from the market in many countries in 2020.

The brand names of the drugs and whether they are on the market can change over time.

Important: Lansor (lansoprazole) is not an H2 blocker. It belongs to a different group of drugs called proton pump inhibitors.

What are they used for?

Gastro-oesophageal reflux

Reflux is the backward flow of stomach contents into the gullet. It can cause burning in the chest and a bitter or sour taste coming up into the mouth.

H2 blockers can be helpful particularly for mild, occasional reflux complaints.

However, if there is marked inflammation or ulceration of the gullet, proton pump inhibitors are generally more effective treatments.

Stomach and duodenal ulcers

By reducing stomach acid, H2 blockers can help some ulcers heal.

Today, proton pump inhibitors are mostly preferred for treating ulcers.

If the ulcer is caused by the bacterium Helicobacter pylori, taking an acid-reducing drug alone is not enough. The bacterium must be treated with the appropriate drugs.

Heartburn at night

In some patients heartburn is particularly marked at night.

H2 blockers can be used to reduce night-time complaints in patients for whom the doctor thinks they are suitable.

However, with regular, continuous use these drugs can lose some of their acid-reducing effect over time. For this reason, long-term use may not be suitable for every patient.

How are H2 blockers taken?

The dose, the time of day it is taken and the length of treatment vary with the disease.

Some patients take it once a day, others at different intervals.

H2 blockers can generally be taken regardless of meals. However, the product information for the drug being used and the doctor’s advice should be followed.

In patients with reduced kidney function, the dose may need adjusting, particularly for famotidine.

The drug should not be taken at high doses or for a long time without a doctor’s advice.

Are H2 blockers the same as antacids?

No.

Antacids neutralise the acid already in the stomach and give short-term relief.

H2 blockers, by contrast, reduce the stomach’s production of new acid. Their effect can last longer than that of antacids.

In some situations they can be taken together. However, depending on the type of antacid, a gap may need to be left between the drugs.

So if you are taking an antacid or another stomach medicine, ask your doctor or pharmacist.

What are the side effects of H2 blockers?

H2 blockers are generally well tolerated.

Possible side effects

• Headache
• Dizziness
• Nausea
• Constipation
• Diarrhoea
• A feeling of discomfort in the abdomen

Less common but important problems

Particularly in elderly patients or those with impaired kidney function, side effects involving the nervous system, such as confusion, can occur.

Rarely, serious allergic reactions or problems with the heart rhythm can develop.

If shortness of breath, swelling of the face or throat, fainting or a marked change in consciousness develops, get emergency medical help.

Do they interact with other medicines?

Yes, some H2 blockers can change the effect of other medicines.

Cimetidine in particular can affect how many medicines are cleared from the body.

In addition, the fall in stomach acid can change how some medicines are absorbed from the bowel.

Patients who take medicines regularly should tell their doctor, particularly if they take blood thinners, epilepsy medicines or medicines used to treat fungal infections.

Who should take them with care?

The choice of drug and the dose should be assessed carefully in the following patients:

• People with kidney disease
• Elderly patients
• People taking more than one medicine
• Pregnant women and breastfeeding mothers
• People who have had an allergy to these drugs before

Also, if there are signs such as difficulty swallowing, unexplained weight loss, vomiting blood, black stools or anaemia, it is not right to simply suppress the complaints with a stomach medicine. These situations need medical assessment.

Frequently asked questions

Are H2 blockers the same as omeprazole and pantoprazole?

No. Omeprazole, pantoprazole and lansoprazole are proton pump inhibitors. These drugs reduce stomach acid by a different mechanism from H2 blockers and generally suppress acid more strongly.

Are H2 blockers addictive?

No. They are not addictive. However, if the underlying disease continues, heartburn can come back when the drug is stopped.

Can H2 blockers be taken for a long time?

Some patients may need long-term use. However, whether the treatment is still needed, the dose and its length should be reviewed at regular intervals.

Do H2 blockers prevent stomach cancer?

No. H2 blockers have not been shown to prevent stomach cancer. Also, an easing of stomach complaints does not prove for certain that there is no serious underlying disease.

Are H2 blockers enough for every reflux patient?

No. They can be helpful for mild complaints. But patients with severe reflux, erosions in the gullet or complications may need other treatments.

Important: This page has been prepared to give general health information. The choice of H2 blocker, the dose and the length of use should be decided according to the patient’s disease, kidney function and other medicines.