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H2 antagonists: Uses, common brands, and safety information

H2 antagonists—also called H2 blockers—are commonly used to treat heartburn and similar conditions

Heartburn, or acid indigestion, is a common condition—affecting about 20% of people in the United States. 

The esophagus carries food and liquids from the mouth to the stomach. Gastroesophageal reflux disease (GERD) occurs when a muscle at the end of the esophagus does not properly close, allowing the stomach contents to leak back into the esophagus. When stomach contents flow back up into the esophagus, symptoms of heartburn occur. 

Heartburn causes an uncomfortable feeling in the middle of the chest, throat, or upper abdomen. Sometimes heartburn causes you to taste food or acidic fluid in the back of the mouth. If you have these symptoms more than two times weekly, you may have GERD

A doctor may recommend trying over-the-counter medication to help heartburn, such as antacids—like Tums (calcium carbonate), Mylanta (aluminum, magnesium, and simethicone), or Rolaids (calcium and magnesium). 

Another common class of drugs for heartburn are proton pump inhibitors (PPIs)—some examples include Prilosec (omeprazole), Nexium (esomeprazole), and Prevacid (lansoprazole). 

H2 antagonists—also called H2 blockers—are another type of drug commonly used for heartburn. H2 antagonists include Tagamet (cimetidine), Axid (nizatidine), and Pepcid (famotidine). In addition to GERD, H2 antagonists treat other indications as well, such as duodenal ulcers or erosive esophagitis. This article will focus on H2 antagonists—their uses, side effects, and other information. Continue reading to learn more about H2 antagonists. 

List of H2 antagonists
Drug name SingleCare savings Learn more
Axid (nizatidine) Get Axid coupons Axid details
Pepcid, Pepcid AC (famotidine) Get Pepcid coupons Pepcid details
Tagamet, Tagamet HB (cimetidine) Get Tagamet coupons Tagamet details

Other H2 antagonists

The U.S. Food and Drug Administration (FDA) removed all Zantac (ranitidine) products from the market in April of 2020 due to N-Nitrosodimethylamine (NDMA) contamination. 

What are H2 antagonists?

H2 antagonists suppress stomach acid and are used to treat or prevent a variety of stomach conditions, such as GERD and ulcers. H2 antagonists are also known as H2 receptor antagonists (H2RAs) or H2 blockers. They are available in brand name and generic formulations, and as prescription and over-the-counter (OTC) drugs. All H2 blockers are similarly effective. 

How do H2 antagonists work?

Normally, after you eat, histamine is released. Histamine then binds to H2 receptors, leading to gastric acid release. H2 antagonists work by binding to histamine H2 receptors on cells in the stomach called gastric parietal cells. By binding to H2 receptors, H2 antagonists prevent histamine from binding to H2 receptors. H2 antagonists provide symptom relief in about an hour and can last for several hours. 

What are H2 antagonists used for?

The indications for each H2 antagonist vary slightly by specific drug. General indications for H2 antagonists are:

  • Gastroesophageal reflux disease (GERD)
  • Prevents and relieves heartburn from acid indigestion and sour stomach
  • Active duodenal ulcer
  • Lower the risk of duodenal ulcer recurrence (maintenance therapy)
  • Active benign gastric ulcer
  • Erosive and ulcerative esophagitis (diagnosed by endoscopy)
  • Pathological hypersecretory conditions such as Zollinger-Ellison syndrome, systemic mastocytosis, or multiple endocrine neoplasias

H2 antagonists may be used off-label for:

Who can take H2 antagonists?

Before taking an H2 antagonist for the first time, see your healthcare provider. He or she will want to review your symptoms, check your health with a physical exam, and decide if any labs or other tests are necessary. At your appointment, tell your doctor about your symptoms, medical conditions, and medications you take. This information will help the doctor decide if an H2 antagonist is safe for you to take, and ensure that there are no drug interactions.


Men can take an H2 antagonist, provided that there are no restrictions for use (see “Restrictions” section below). 


Women who are not pregnant or breastfeeding can take an H2 antagonist, as long as there are no restrictions for use. Check with your doctor before starting an H2 antagonist if you are pregnant or breastfeeding. 


Consult a pediatrician for medical advice regarding H2 antagonist use in a child. 

  • Famotidine is approved for use in children for peptic ulcer disease or GERD
  • Nizatidine is approved for GERD and erosive esophagitis in adolescents 12 years and older (and may be used off-label in children ages 6 months to 11 years old).
  • Cimetidine is not recommended in children under age 16 years.


Older adults should check with their doctor before using an H2 antagonist. H2 antagonists should be used with caution in older adults, and the lowest effective dose should be used. Kidney function should be monitored while taking an H2 antagonist.

Are H2 antagonists safe?



Patients who are allergic to an H2 antagonist should not take any H2 antagonist. 

Before taking an H2 antagonist, tell your doctor or healthcare provider if you are immunocompromised or if you have: 

  • Kidney, lung, or liver problems
  • Diabetes
  • Wheezing
  • Unexplained weight loss
  • Nausea, vomiting, or stomach pain
  • Heartburn for more than three months
  • Lightheadedness, sweating, dizziness, chest or shoulder pain, shortness of breath, sweating

Tell your doctor about all of the medications you take, including prescriptions, OTC, vitamins, and supplements.

Patients who are taking an OTC H2 antagonist and have pain with swallowing, vomiting with blood, or black/bloody stools should stop taking the medication and seek medical treatment. 

Are H2 antagonists controlled substances?

No, H2 antagonists are not controlled substances.

Common H2 antagonists side effects

The most common side effects of H2 antagonists are:

  • Headache 
  • Drowsiness 
  • Dizziness 
  • Rash 
  • Altered taste
  • Stomach pain, diarrhea, or constipation

People with kidney or liver problems or who are over 50 years old have more adverse effects such as delirium, confusion, hallucinations, or slurred speech. 

Allergic reactions to H2 antagonists are rare. If you experience symptoms of an allergic reaction such as hives, trouble breathing, or swelling around the face, lips, tongue, or throat, get emergency medical help right away. 

Side effects vary by drug. This is not a full list of side effects. Consult your doctor for a full list of side effects. Report side effects or anything that concern you to your doctor. 

How much do H2 antagonists cost?

H2 antagonists are relatively inexpensive, especially when you choose the generic version. Using a free SingleCare card, too, can help you save even more. SingleCare coupon users can save up to 80% on the cost of medications. If you are using an OTC H2 antagonist, you’ll also need a prescription from your doctor in order to use the SingleCare card or coupon.