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
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.
Few side effects happen with short-term use of H2 blockers. Side
effects may include:
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
Some people find that taking a single bedtime dose of an H2 blocker
effectively relieves their symptoms. This schedule is also very
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
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Brown TJ, et al. (2006). A comparison of the cost-effectiveness of five strategies for the prevention of non-steroidal anti-inflammatory drug-induced gastrointestinal toxicity: A systematic review with economic modelling. Health Technology Assessment, 10(38): iii-vii, ix-xiii, 1-420.