H2 Blockers

Class of Drugs that Block Stomach Acid

H2 blockers, also called H2-receptor antagonists, are medicines that reduce the amount of acid the stomach produces by blocking one important producer of acid: histamine2.

Histamine2, a common chemical in the body, signals the stomach to make acid. H2 Blockers oppose histamine’s action and reduce the amount of acid the stomach produces. This type of medication is used to treat conditions in which the stomach produces too much acid, such as gastroesophageal reflux disease. They also have been prescribed for the treatment of peptic ulcer symptoms.

How Do H2 Blockers Work?

A cell in the stomach, called a parietal cell, makes acid. These cells, found in the stomach lining, are stimulated in a number of ways to produce acid. One of these methods is histamine. H2 Blockers reduce acid production by blocking signals that tell the stomach to make acid. Their four drugs that work by this mechanism in the United States are Zantac (ranitidine), Pepcid (famotidine), Tagamet (cimetidine) and Axid (nizatidine).

What Are H2 Blockers Used for?

They are used for the treatment of symptoms of gastroesophageal reflux disease, and for the treatment of esophagitis. They have also been used in combination with antibiotics for the treatment of peptic ulcers.

Are there Differences Among the Different H2 Blockers?

There are differences in potency. Over-the-counter formulations are the least potent doses. Among the prescription forms, Pepcid (famotidine) is the most potent H2 Blocker. The main differences between H2 Blockers is the interaction each has with other medications a patient may be taking.

What are the different types of H2 Blockers?

Prescription forms:

• Tagamet (cimetidine)
• Pepcid (famotidine)
• Axid (nizatidine)
• Zantac (ranitidine)

Nonprescription (over the counter) forms:

• Tagamet-HB
• Pepcid-AC
• Axid AR
• Zantac 75

How Are H2 Blockers Different from Proton Pump Inhibitors (PPIs)?

Both PPIs and H2 blockers suppress gastric acid secretion, but at different stages of produciton.. While histamine blockers block one of the first stimuli for acid production, proton pump inhibitors block the final step in the pathway of acid secretion in the stomach, resulting in greater suppression of acid. PPIs shut down the proton pumps in the stomach, H2 blockers work by blocking the histamine receptors in acid producing cells in the stomach. PPIs have a delayed onset of action, while H2 Blockers begin working within an hour. PPIs work for a longer period of time; most up to 24 hours and the effects may last up to three days. H2 Blockers, however, usually only work up to 12 hours.


For more information about the individual H2 blocker medications, please check out the resources below.

• Axid

• Pepcid

• Tagamet

• Zantac

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_{Sources:
"Pharmacodynamic Aspects of Hz-Blockers versus proton Pump Inhibitors." U.S. Food and Drug Administration. 26 Apr 2007}

"Understanding Some of the Medications Often Prescribed for GERD & Ulcers." Common GI Problems: Volume 1. American College of Gastroenterology. 26 Apr 2007

Kenneth R. DeVault M.D., F.A.C.G., and Donald O. Castell M.D., M.A.C.G., "Updated Guidelines for the Diagnosis and Treatment of Gastroesophageal Reflux Disease." doi: 10.1111/j.1572-0241.2005.41217.x. American College of Gastroenterology. 24 Apr 2007

"Effectiveness of Therapies for GERD" American College of Gastroenterology. 26 Apr 2007