If you have heartburn, you may be interested in learning about famotidine. It’s a generic prescription drug used to treat the following in adults and some children:

The drug is also used in adults to:

  • treat conditions that cause the stomach to make too much acid
  • prevent ulcers in the intestines if a person has had an ulcer in the past

Famotidine comes as an oral tablet (a tablet that you swallow). Pepcid AC and Zantac 360 are brand-name versions of this drug. These versions may be available over the counter as well as by prescription. Famotidine also comes in an injectable form, an oral suspension (a kind of mixture in liquid), and a chewable tablet.

You may take famotidine short term or long term, depending on your condition. Your doctor will recommend the best treatment plan for you.

This article describes famotidine’s side effects, also known as adverse effects. For more information about famotidine, including details about its uses, see this in-depth article.

Some people may have mild to serious side effects during their famotidine treatment. Examples of famotidine’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

You may have mild side effects from taking famotidine. Examples of mild side effects that have been reported with famotidine include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking famotidine unless your doctor recommends it.

Famotidine may cause mild side effects other than the ones listed above. See the drug’s prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with famotidine, visit MedWatch.

Serious side effects aren’t common with famotidine, but they can occur. Serious side effects that have been reported with famotidine include:

* To learn more about this side effect, see the “Side effects explained” section below.

If you develop serious side effects while taking famotidine, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Get answers to some frequently asked questions about famotidine’s side effects.

Is the risk of side effects from famotidine lower with the 20-mg dose than with the 40-mg dose?

Yes, it’s possible that your risk of side effects from famotidine 20 milligrams (mg) may be lower than that from famotidine 40 mg. This is because taking a lower dose of a drug means less of it in your body. As a result, your risk of side effects will likely decrease.

If you have questions about the risk of side effects from your dose of famotidine, ask your doctor or pharmacist.

Does famotidine cause long-term side effects?

Although rare, famotidine can cause long-term side effects. Examples of long-term side effects that can occur from taking famotidine include:

If you have concerns about famotidine causing long-term side effects, talk with your doctor. They can recommend ways to prevent certain long-term side effects. They may also monitor you more closely for symptoms of such side effects during treatment.

Is famotidine known to cause weight gain or hair loss?

No, famotidine isn’t known to cause weight gain or hair loss. These side effects weren’t reported in studies of people taking famotidine.

If you notice weight gain or hair loss during your treatment with famotidine, talk with your doctor. They’ll try to determine what could be causing your weight gain or hair loss. They may also recommend ways to help manage these effects.

Learn more about some of the side effects famotidine may cause.

Nausea

You may develop nausea from taking famotidine, although this side effect didn’t happen often in studies.

What might help

If you have nausea from taking famotidine, talk with your doctor. They can make recommendations for how to best manage this side effect. For example, taking medications with food may help decrease your nausea.

For remedies that may ease nausea, check out this article. You and your doctor can discuss whether any of these remedies are safe for you to try.

Headache

Famotidine can cause headaches. In studies of the drug, headaches were a commonly reported side effect.

What might help

If you have headaches during your treatment with famotidine, tell your doctor. They may be able to recommend ways to treat this side effect. For example, taking over-the-counter medications, such as Tylenol (acetaminophen) or Advil (ibuprofen), may help ease headache pain.

For a few at-home headache remedies, check out this article. You can ask your doctor whether these remedies are appropriate for you to try.

Dry mouth

You may develop a dry mouth from taking famotidine. But in studies of the drug, this was not a common side effect.

What might help

If you have a dry mouth from taking famotidine, tell your doctor. They can recommend ways to manage it. Examples include using certain kinds of mouthwash or lozenges to treat this side effect. This article has several other tips for easing a dry mouth.

Thrombocytopenia

Famotidine can cause thrombocytopenia, which refers to a low blood level of platelets. Platelets are a kind of cell that helps your blood clot. In studies of the drug, this wasn’t a commonly reported side effect.

Symptoms of thrombocytopenia include:

What might help

If you develop symptoms of thrombocytopenia, tell your doctor. They’ll check your blood to be sure that your platelets aren’t too low.

If you do develop thrombocytopenia, your doctor may closely monitor your platelet levels while you’re taking famotidine. In some cases, they may recommend a different treatment option for you.

Heart palpitations

It’s possible to develop heart palpitations from taking famotidine, although this side effect didn’t occur often in studies.

Symptoms of heart palpitations include:

  • feeling like your heart is fluttering or has skipped a beat
  • fast heart rate

What might help

If you think you’re having heart palpitations, tell your doctor. They may do some tests on your heart to be sure that it’s beating properly. In some cases, they may recommend a treatment option other than famotidine for you.

Allergic reaction

Like most drugs, famotidine can cause an allergic reaction in some people.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to famotidine, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to famotidine, they may have you switch to a different treatment.

Keeping track of side effects

During your famotidine treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how famotidine affects you. They can then use this information to adjust your treatment plan if needed.

Famotidine may not be right for you if you have certain medical conditions. These are known as drug-condition interactions. Other factors may also affect whether famotidine is a good treatment option for you.

Talk with your doctor about your health history before starting famotidine. Factors to consider include those described below.

Kidney problems. Kidney problems may increase your risk of side effects from taking famotidine. If you have kidney problems, tell your doctor before you start famotidine treatment. They may recommend that you take a lower dose of the drug or, in some cases, avoid using the drug.

Allergic reaction. If you’ve had an allergic reaction to famotidine or any of its ingredients, your doctor will likely not prescribe this drug. Ask them what other medications are better options for you.

Age. People ages 65 years and older may have an increased risk of side effects from taking famotidine. If you’re an older adult, your doctor may recommend taking a lower dose of this drug due to this risk.

Alcohol and famotidine

There aren’t any known interactions between alcohol and famotidine. But alcohol can increase the risk of side effects from famotidine.

Both famotidine and alcohol may cause:

Drinking alcohol during famotidine treatment may increase your risk of these side effects.

In addition, alcohol may make symptoms of gastroesophageal reflux disease (GERD) worse. If you’re taking famotidine to treat GERD, drinking alcohol may worsen your condition.

If you’d like to drink alcohol while taking famotidine, talk with your doctor. They can let you know how much alcohol, if any, is safe to consume.

Pregnancy and breastfeeding while taking famotidine

It’s not known whether it’s safe to take famotidine during pregnancy or while breastfeeding.

At this time, there isn’t enough information to determine whether this drug increases the risk of fetal harm or pregnancy loss.

Famotidine may pass into breast milk. But it’s unclear what effects the drug may have on a child who is breastfed or on breast milk supply.

If you’re pregnant, breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor before taking famotidine. They can answer any questions about using famotidine during these times.

Famotidine may cause side effects. While these tend to be mild, severe side effects are also possible.

If you have any questions about the side effects famotidine can cause, ask your doctor. Knowing what side effects the drug can cause can help you and your doctor decide whether this treatment is right for your condition.

Here are some questions to help get you started:

  • Do I have an increased risk of side effects from famotidine due to other medications I take?
  • Is my risk of side effects higher when I first start treatment with famotidine?
  • How do the side effects of famotidine compare with other drugs that can treat my condition?

You might also want to ask your doctor about Pepcid AC or Zantac 360, which are the brand-name versions of famotidine. A generic drug and its brand-name version are expected to have the same side effects because they contain the same active ingredient. (An active ingredient is what makes a drug work.)

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.