Famotidine: uses, side effects, and dosage

Famotidine is a medication that blocks acid production in the stomach. 

Your stomach uses powerful hydrochloric acid to help you digest the food you eat. But it makes acid all the time, even when you aren’t eating. Seeing, smelling, and even just thinking about food is enough to get the acid flowing. 

Certain things––like spicy or fatty foods, caffeine, and alcohol––increase stomach acid production. These triggers also weaken the muscles that keep acid from flowing back up your esophagus. Many of us are all too familiar with this painful, burning sensation known as heartburn or acid reflux. 

When this unpleasant feeling occurs, famotidine can be used to alleviate the symptoms.

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Famotidine is a type of medication called a histamine-2 receptor antagonist, or H2-blocker for short. 

As its name indicates, H2-blockers bind to special structures in the stomach called the H2-receptors. When H2-receptors are blocked, your stomach produces less acid. 

Managing stomach acid production is especially important for those living with stomach-related conditions like chronic heartburn, gastroesophageal reflux disorder (GERD), ulcers, and more. Famotidine is available in varying dosages under different brand names, including Pepcid, Pepcid AC, and Zantac 360.

Famotidine is approved by the U.S. Food and Drug Administration (FDA) for the following conditions (FDA, 2018):

• Acid reflux: People with reflux experience frequent heartburn from acid rising back up from the stomach into the esophagus, the tube that connects your mouth to your stomach. Famotidine decreases the amount of stomach acid, which relieves the symptoms of reflux (also known as GERD or gastroesophageal reflux disease).

• Ulcers: Too much stomach acid can wear away at the stomach and intestinal lining, causing erosions or ulcers (also called peptic ulcer disease). Famotidine is used to help treat both stomach ulcers and ulcers that appear further down your digestive system.

• Esophagitis: Over time, GERD can irritate the lining of the esophagus, causing inflammation there known as esophagitis. Famotidine helps relieve esophagitis by reducing the among of acid there and alleviating symptoms like heartburn. 

• Zollinger-Ellison syndrome: Zollinger-Ellison syndrome is a rare condition where the stomach makes so much acid that ulcers develop along the digestive tract. Because famotidine decreases acid production, it effectively treats the symptoms of this uncommon condition. 

Famotidine is also used off-label for certain conditions. Off-label medications are not specifically approved by the FDA for the condition being treated, but healthcare providers can prescribe them if they feel it’s the appropriate treatment for their patients. Off-label uses for famotidine include: 

• Irritation from NSAIDs: Non-steroidal anti-inflammatory drugs (NSAIDs) are medications like the common painkillers aspirin and ibuprofen. When used for extended periods of time, these drugs can irritate the stomach lining and even cause ulcers. (Deeks, 2013).  

• Stress ulcers: Stress also has a big impact on our bodies. Research has found that people being treated in intensive care units (ICUs) are at risk of developing stomach ulcers due to stress. Famotidine is used off-label to prevent ulcers in these patients. 

• COVID-19: Famotidine has been used along with antiviral medications to treat COVID. One clinical trial suggests this combination lowers the risk of severe disease and death (Mather, 2020).  

Famotidine is safe and well-tolerated. Common side effects of famotidine include dizziness, headaches, diarrhea, and constipation (FDA, 2018).

Serious side effects aren’t seen as often, but here are ones to be aware of: 

• Infection in children: Kids who take acid reducers like famotidine might have a higher risk of infections like stomach viruses or pneumonia (lung infections) (Canani, 2006). 

• Intestinal infection: People taking famotidine have a higher chance of getting Clostridium difficile, a type of bacteria that causes a serious intestinal infection (Nath, 1994). 

• Nervous system symptoms: H2-blockers like famotidine can affect the brain, causing nervous issues like seizures (Cannon, 2004). 

• Cardiac symptoms: People who take H2-blockers have an increased risk of arrhythmias (abnormal heart rhythms), including a condition called long-QT syndrome (Yun, 2015). 

• Liver damage: All H2-blockers have been linked to liver damage, although cases are rare. Issues with the liver are seen more often in other H2-blockers than famotidine. 

Famotidine is available over-the-counter as a tablet and in liquid form in doses of 10 mg, 20 mg, and 40 mg. You can also get a chewable version combined with antacids like calcium under the brand name Pepcid Complete. 

Famotidine is also available as an intravenous (IV) solution at some healthcare facilities. 

People with acute (sudden, short-term) acid reflux usually start famotidine at a dosage of 10-20 mg once a day. People with GERD usually start taking 20 mg at bedtime. A healthcare provider might recommend higher dosages for conditions like ulcers or esophagitis. 

Famotidine isn’t typically for long-term use, so consult your healthcare provider before taking it. 

Why take famotidine at night?

If you think your acid reflux symptoms are worse at night, it’s not your imagination—there are biological reasons for this. 

Your stomach produces more acid late at night, and when you lay down flat to sleep, it’s easier for acid to flow up towards your throat. Many healthcare providers recommend taking acid reducers like famotidine at bedtime to prevent this (Voigt, 2019).

Because of how H2-blockers work, they can affect the concentration of other medications you’re taking, potentially resulting in additional side effects. 

This happens much less with famotidine compared to other H2-blockers but can still impact the metabolism of medications, including:

• Atazanavir, an HIV medication (Wang, 2011)

• Itraconazole, an antifungal medication (Lim, 1993)

• Doxorubicin, a chemotherapy drug (Hegazy, 2021)

Some people are at higher risk for adverse effects when taking famotidine, including: 

• People with an allergy to this or similar medications: If you’ve had an allergic reaction to H2-blockers in the past avoid taking famotidine. 

• Those with certain symptoms: If you’re experiencing serious health symptoms like chest pain, wheezing, bloody stool, or significant unintended weight loss, follow up with a healthcare provider before starting medications like famotidine. 

• Underlying medical conditions: Since famotidine is broken down in the liver and filtered by the kidneys, people with liver or kidney disease might not be able to take it. Consult a healthcare professional before taking this drug. 

Pregnancy and breastfeeding

Studies suggest that famotidine is not associated with any pregnancy complications. So far there’s no evidence it causes infant death, premature birth, or adverse effects during pregnancy (Matok, 2010). 

Famotidine is also safe during breastfeeding since the baby receives less than 2% of what’s in your breast milk––this is less than the recommended dosage given to infants with reflux (LactMed, 2021). A healthcare provider can advise you about safely taking medications while pregnant or breastfeeding. 

If you have any questions about famotidine, what it’s used for, or when to take it, reach out to your healthcare provider or pharmacist.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

January 04, 2022

Written by

Gina Allegretti, MD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.