H2 blockers are a class of medications used to treat heartburn and other symptoms of gastroesophageal reflux (GERD) and peptic ulcers.

These medications work by reducing the amount of stomach acid secreted by glands in the lining of your stomach. There are several types of H2 blockers that are sold under different brand names. These include the following:

  • Cimetidine (Tagamet®)
  • Famotidine (Pepcid®)
  • Nizatidine (Axid®)
  • Ranitidine (Zantac®)

The different H2 blockers tend to be equally effective at relieving symptoms, but individuals may have a different experience with different formulations and side effects may vary.

Taking H2 blockers

H2 blockers are most often taken by mouth and are found as tablets, liquids, or capsules.

  • The most common way of taking them is with the first meal of the day.
  • It takes 30 - 90 minutes for the medication to start working, but the benefits last for hours.
  • People often take the drugs at bedtime too.
  • Symptoms may improve for up to 24 hours after taking the drug.

H2 blockers may be bought in lower doses at the store without a prescription.

If you find yourself taking these most days for acid reflux symptoms for 2 weeks or more, make sure you see your health care provider about your symptoms.

Side effects from H2 Blockers

Side effects from H2 blockers are rare, but may include headache, diarrhea or dizziness.

If you are breastfeeding or pregnant, talk to your health care provider before taking these medications. Anyone with kidney problems should use famotidine only under a doctor's direction.

Tell your health care provider if you are taking other medicines. H2 blockers may change the way certain drugs are absorbed or work.


This information is for general educational uses only. It may not apply to you and your personal medical needs. This information should not be used in place of a visit, call, consultation with or the advice of your physician or health care professional.

Communicate promptly with your physician or other health care professional with any health-related questions or concerns.

Be sure to follow specific instructions given to you by your physician or health care professional.

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