H2 Receptor Antagonists

What are H2 receptor antagonists?

H2 receptor antagonists, also called H2-blockers, are taken to relieve pain and injury associated with excessive stomach acid production. Some conditions cause stomach acid to move in the wrong direction (out of your stomach) and into your esophagus, which is the tube that moves food from your mouth to your stomach. This can cause symptoms of sore throat, coughing, bitter taste, bad breath, and heartburn, a burning sensation in your chest or throat that can occur after eating. H2-blockers are available as oral tablets or capsules, chewable or dissolvable tablets, liquid, powders, and injectable solutions that are given intravenously (into a vein in your arm) by a healthcare professional. Types of H2-blockers that are available include famotidine (Pepcid, Pepcid AC), cimetidine (Tagamet, Tagamet-HB), nizatidine (Axid, Axid AR), and ranitidine (Zantac, Zantac 75). These medications are available over-the-counter and by prescription.

What are H2 receptor antagonists used to treat?

H2-blockers relieve heartburn associated with sour stomach and acid indigestion. They are used to treat gastroesophageal reflux disease (GERD) and conditions that cause too much stomach acid to be produced. H2-blockers can also be used as part of a treatment plan to heal stomach ulcers and damage to the esophagus caused by long-term exposure to stomach acid.

What is GERD?

There is a group of muscles located at the end of your esophagus, called the lower esophageal sphincter [LES], which separates your esophagus from your stomach. The LES normally opens to let food enter the stomach, and closes to prevent any stomach contents from reaching your esophagus. The stomach has a mucus lining to protect it from the corrosive properties of stomach acid, but the esophagus does not have this lining. Instead, the esophagus relies on the proper functioning of the LES to protect it from exposure to stomach acid. In GERD, the LES relaxes or weakens, allowing the contents of the stomach to flow up into the esophagus. When stomach acid reaches your esophagus, it can cause heartburn and other symptoms. GERD can occur during pregnancy due to the extra pressure in your abdomen from your growing baby. You can read more about GERD during pregnancy here.

How do H2 receptor antagonists work?

H2-blockers work by blocking the effects of histamine in the cells in your stomach. Histamine normally attaches to stomach cells and promotes the release of stomach acid. By blocking the effects of histamine, H2-blockers prevent the release of stomach acid. This reduces the amount of acid in your stomach, which improves symptoms of heartburn and acid indigestion. In addition, by reducing the amount of stomach acid, H2-blockers can help heal ulcers and injury to the esophagus.

If I am taking an H2 receptor antagonist, can it harm my baby?

The FDA recommends that H2-blockers should only be used during pregnancy if medically necessary, as determined by your doctor. Although some studies have not found a link between H2-blockers taken during pregnancy and birth defects, one study found that there was a higher risk of premature birth in babies whose mom used an H2-blocker while pregnant. Some studies have also found that taking an H2-blocker during pregnancy can increase the risk that your baby will develop childhood asthma.

Evidence:

A large study that looked at 2,398 babies who were exposed to an H2-blocker during pregnancy found that H2-blockers were not associated with a higher risk of birth defects. They also found no increased risk of birth defects, premature birth, miscarriage, or intrauterine growth restriction (when babies are born smaller than normal for their age) in expecting moms who used an H2-blocker. The study concluded that H-2 blockers can be used safely in pregnancy to manage heartburn and GERD.

One of the studies that was analyzed by the review above looked at 553 expecting moms who took an H2-blocker during pregnancy. They found that there was a higher risk of premature birth in expecting moms who took an H2-blocker, but no increased risk of birth defects. Another study looked at 1,148 expecting moms who took an H2-blocker during pregnancy. They found no increased risk of birth defects, premature birth, low birth weight, or death of the baby.

Although some studies have not found an increased risk of birth defects or birth complications in babies exposed to H2-blockers during pregnancy, some studies have found that the use of medications that reduce stomach acid, including H2-blockers, can increase the risk that your baby will develop childhood asthma. One study looked at 1,414 babies whose mom took an H2-blocker while pregnant. These babies were found to have a higher risk of childhood asthma. More studies are needed to determine if taking medications that decrease stomach acid during pregnancy increases the risk that your baby will develop childhood asthma.

Bottom line: H2-blockers should be avoided during pregnancy unless medically necessary, as determined by your doctor. Many studies have not associated these medications with an increased risk of birth defects; however, there is concern that medications that lower stomach acid may increase your babys risk for developing childhood asthma. One study also found that these medications increased the risk of premature birth.

If I am taking an H2 receptor antagonist and become pregnant, what should I do?

If you become pregnant while taking an H2-blocker, you should contact your doctor immediately. Your doctor may decide to discontinue your medication until after the birth of your baby.

If I am taking an H2 receptor antagonist, can I safely breastfeed my baby?

The FDA recommends that moms should not breastfeed if taking cimetidine, famotidine, or nizatidine; it is recommended to use caution when nursing moms are taking ranitidine. Despite the FDA recommendations, the American Academy of Pediatrics has classified cimetidine as usually compatible with breastfeeding. There is almost no data available on the safety of H2-blockers in the breastfed baby. H2-blockers pass into breast milk and have the potential to cause digestive issues and problems with the babys ability to metabolize medications. One case report described a baby whose mom used ranitidine twice daily for 2 days. There were no health problems observed in the baby.

Bottom line: H2-blockers should be avoided while breastfeeding. There is very little data available on the safety of these medications in the breastfed baby. These medications pass into breast milk and have the potential to cause health problems in your baby.

If I am taking an H2 receptor antagonist, will it be more difficult to get pregnant?

There are no studies discussing the effects of H2-blockers on fertility in women. However, some animal studies have shown that H2-blockers have anti-fertility properties and can prevent implantation of a fertilized egg in females. In addition to the effects observed in female animals, H2-blockers may impair fertility in men. A study found that cimetidine negatively affected semen quality, which could potentially impair fertility in some men. Famotidine did not seem to affect semen quality, and the effects of ranitidine and nizatidine on semen quality are unclear. H2-blockers can also cause loss of sexual function in men. You should contact your doctor if you are planning to become pregnant while taking an H2-blocker. In addition, your male partner may wish to contact his doctor prior to trying to conceive.

If I am taking an H2 receptor antagonist, wh
at should I know?

H2-blockers should not be used during pregnancy unless medically necessary. Although many studies have not found an increased risk of birth defects or other birth complications with the use of H2-blockers during pregnancy, one study found that these medication increased the risk of premature birth. In addition, some studies have shown that H2-blockers increase the risk that your baby will develop childhood asthma.

H2-blockers should not be used while breastfeeding. These medications pass into breast milk and have the potential to cause harm to your baby. There is almost no data available on the safety of these medications while breastfeeding.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of H2 receptor antagonists during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry’s expert report about GERD here.  Additional information can also be found in the links below. 

Resources for H2 receptor antagonists during pregnancy and breastfeeding:

For more information about H2 receptor antagonists during and after pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or check the following links:

1. National Institute of Diabetes and Digestive and Kidney Diseases (2014). Symptoms and Causes of GER & GERD.

4. WebMD (2017). How Acid Reducers Can Help Treat Heartburn. Accessed: March 21, 2018.