Digestive Disorders Health Center

Examples

Histamine H2 acid reducers (commonly called H2 blockers) are available in nonprescription and prescription forms.

H2 blockers are usually taken by mouth, although some can also be given as an injection. Two doses (morning and evening) are generally recommended to control both daytime and nighttime symptoms. Doctors sometimes recommend a single dose, taken at bedtime.

How It Works

H2 blockers decrease the production of stomach acid, which may reduce irritation to the stomach lining and help an ulcer heal.

Why It Is Used

H2 blockers often are used to treat a peptic ulcer or symptoms of indigestion (dyspepsia). Serious complications from these drugs are uncommon.

H2 blockers are sometimes used to prevent ulcers in people who take NSAIDs long-term (for example, for arthritis).

How Well It Works

H2 blockers are often effective treatments for indigestion or heartburn. All four appear to work equally well.

H2 blockers are often able to control the symptoms of an ulcer. But they cannot cure an ulcer that is caused by an infection with H. pylori bacteria. H2 blockers are sometimes used in combination with antibiotics to treat H. pylori infections.

H2 blockers can help prevent ulcers caused by daily long-term NSAID use.¹

H2 blockers work better than antacids but not as well as proton pump inhibitors (PPIs) to control symptoms of ulcers and prevent new ulcers.

Side Effects

Few side effects happen with short-term use of H2 blockers. Side effects may include:

• A headache.
• Dizziness.
• Diarrhea.
• Constipation.
• Nausea.
• Vomiting.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Antacids and H2 blockers should not be taken within 2 hours of each other, because the antacid will cause the H2 blockers to take effect more slowly.

Some people find that taking a single bedtime dose of an H2 blocker effectively relieves their symptoms. This schedule is also very convenient.

H2 blockers are generally thought to be safe for pregnant women to use. But discuss this with your doctor if you want to use them during pregnancy.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.