How does this medication work? What will it do for me?

Famotidine belongs to a class of medications called H2antagonists. It is used to treat stomach and duodenal (intestinal) ulcers, gastroesophageal reflux disease (GERD), and conditions where too much stomach acid is secreted, such as Zollinger-Ellison syndrome. It works by reducing the amount of acid secreted by the stomach.

The over-the-counter form of famotidine is used to treat conditions where a reduction of stomach acid is needed, such as acid indigestion, heartburn, or sour or upset stomach. It can also be used to prevent these symptoms when they are associated with eating food or drinking beverages, including nighttime symptoms.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are using this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

This medication is available as 10 mg, 20 mg, and 40 mg tablets.

How should I use this medication?

Tablets: The usual adult dose of famotidine tablets ranges from 20 mg or 40 mg at bedtime to 20 mg or 40 mg twice daily, depending on the condition being treated. This medication can be taken with or without food. Seniors and those with decreased kidney function may require lower doses or longer intervals between doses.

  • The dose of famotidine for treatment of duodenal ulcer is 40 mg at bedtime for 4 to 8 weeks, or less if healing occurs. Therapy is often continued after healing of the ulcer at a dose of 20 mg once daily for up to 6 to 12 months.
  • The usual dose for treatment of benign stomach ulcer is 40 mg once a day at bedtime for 4 to 8 weeks, or less if healing occurs.
  • For Zollinger-Ellison syndrome and similar conditions, the dose varies with the individual patient, but often starts with 20 mg every 6 hours.
  • When used to relieve the symptoms of GERD or prevent GERD from returning, the usual dose is 20 mg twice daily. When used to treat esophageal damage related to GERD, the usual dose is 40 mg twice daily.

When used over-the-counter to treat acid indigestion, heartburn, or sour or upset stomach, the usual dose for adults and children 12 years of age or older is 10 mg to 40 mg once daily. To prevent symptoms brought on by consuming food or beverages, take the dose 10 to 15 minutes before eating food or drinking beverages that are expected to cause symptoms. The maximum dose is 40 mg every 24 hours. Do not take it in this manner for more than 2 weeks without seeking medical advice.

Injection: The injectable form of famotidine may be used in hospitals under specific circumstances when the patient is not able to swallow tablets. The usual dose of famotidine injection is 20 mg every 12 hours given intravenously (into a vein).

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to use this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Store the injection in the refrigerator between 2°C and 8°C, protect it from light, and do not allow it to freeze. Keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to famotidine or any ingredients of the medication
  • are allergic to other acid-reducing agents known as H2-receptor antagonists (e.g., ranitidine, cimetidine, nizatidine)

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • constipation
  • diarrhea
  • dizziness
  • headache
  • nausea
  • tiredness
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • joint pain
  • skin rash
  • symptoms of liver problems (e.g., abdominal pain, fatigue, flu-like symptoms, light coloured stools, nausea, yellowing of the skin or eyes, vomiting)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • symptoms of an allergic reaction (e.g., difficulty breathing or swallowing; swelling of the hands, feet, ankles, face, lips, mouth, or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Kidney disease: Famotidine is eliminated from the body mostly by the kidney. If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Lower doses or longer intervals between doses may be needed.

Severe stomach problems: If you have recurrent vomiting, difficulty swallowing, blood in the stool, significant unintentional weight loss, fatigue (anemia), or are coughing up blood, check with your doctor right away.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Famotidine passes into breast milk. If you are a breast-feeding mother and are taking famotidine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children. For the over-the-counter form, the safety and effectiveness of using this medication have not been established for children under 12 years of age.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Kidney disease: Famotidine is eliminated from the body mostly by the kidney. If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Lower doses or longer intervals between doses may be needed.

Severe stomach problems: If you have recurrent vomiting, difficulty swallowing, blood in the stool, significant unintentional weight loss, fatigue (anemia), or are coughing up blood, check with your doctor right away.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Famotidine passes into breast milk. If you are a breast-feeding mother and are taking famotidine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children. For the over-the-counter form, the safety and effectiveness of using this medication have not been established for children under 12 years of age.

What other drugs could interact with this medication?

There may be an interaction between famotidine and any of the following:

  • atazanavir
  • azole antifungals (itraconazole, ketoconazole, posaconazole)
  • bosutinib
  • cefuroxime
  • dabrafenib
  • dasatinib
  • delaviridine
  • erlotinib
  • mesalamine
  • methylphenidate
  • nelfinavir
  • nilotinib
  • ponatinib
  • rilpivirine
  • risedronate (delayed-release)
  • varenicline
  • vismodegib

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.