• Famotidine decreases the amount of acid the stomach produces and is used to treat certain gastrointestinal conditions characterized by high acid production.
• Famotidine reduces the secretion of gastric acid in the stomach by blocking the effect of histamine on histamine H2-receptors located on the parietal cells lining the stomach wall. Histamine is the chemical transmitter that stimulates the parietal cells to release gastric acid. By blocking H2 receptors, famotidine prevents histamine from having this effect, thereby reducing gastric acid secretion.
• Famotidine is specific for H2 receptors (other drugs, called antihistamines, block H1 receptors that are primarily involved with allergic-type reactions).
• Famotidine belongs to a group of drugs known as H2 receptor antagonists (also called H2 blockers).

• Used for the short-term treatment of active duodenal or gastric ulcers.
• May be used for up to 1 year for the maintenance treatment of healed duodenal or gastric ulcers.
• Reduces stomach acid secretion so may be used in the treatment of gastroesophageal reflux disease (GERD) or hypersecretory conditions such as Zollinger-Ellison syndrome or systemic mastocytosis.
• May also be used in the treatment and maintenance of endoscopically diagnosed erosive esophagitis.
• Famotidine may be sold over-the-counter in approved packaging which means adults and children older than 12 years may self-medicate with famotidine for mild gastrointestinal complaints such as occasional heartburn, indigestion, or sour stomach brought on by certain foods.
• May be less likely to interact with other medications than some other H2 blockers.
• May be used in addition to antacids.
• Generic famotidine is available.

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• A headache and gastrointestinal side effects (such as constipation, diarrhea, nausea, and abdominal pain) are the most common side effects. Other side effects are uncommon in adults.
• People with moderate and severe renal impairment and seniors may be more likely to develop central nervous system (CNS) adverse reactions, such as agitation, confusion, delirium, disorientation, hallucinations, lethargy, and seizures.
• A response to famotidine does not mean that your symptoms are not due to gastric or duodenal cancer (stomach cancer affects approximately 28,000 people in the U.S. each year; the risk is higher in older people). Endoscopy is the only way to check that you do not have stomach cancer; ask your doctor about further investigations if your symptoms persist.
• The dosage of famotidine should be adjusted in people with moderate kidney disease. No data are available to make recommendations about dosage in people with liver disease.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

• May be taken with or without food. Take with a glass of water and take the exact dosage as directed on the packet (self-medicating) or by your doctor (prescribed).
• Should only be taken for short periods. If you feel you need to keep taking famotidine, talk with your doctor.
• Antacids may be taken alongside famotidine if needed for gastric-acid-associated pain.
• Do not self-medicate with famotidine if you are over the age of 40 and this is the first time you have had heartburn or indigestion; have a family history of gastric cancer; have coughing spells; use NSAIDs anti-inflammatories (such as aspirin or ibuprofen); have difficulty or pain when swallowing; already take other drugs (other than antacids) for indigestion or heartburn; are pregnant or breastfeeding or have blood in your vomit or stools. Instead, make an appointment with your doctor.
• Some symptoms of stomach cancer may be similar to heartburn. Seek medical advice if your symptoms are persistent or severe.

• Starts to suppress gastric acid within an hour of taking it. The maximum effect depends on the dose and occurs within one to three hours. The effect of famotidine lasts for 10 to 12 hours after a single dose.
• Peak effects are reached within one to three hours of taking a dose. Symptomatic relief for GERD occurs within 24 hours after starting therapy with famotidine.
• One dose of famotidine substantially inhibits the secretion of gastric acid for 10 to 12 hours.
• Food does not appear to affect the absorption of famotidine or peak concentrations.

Medicines that interact with famotidine may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with famotidine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with famotidine include:

• anticoagulants (blood thinners), such as warfarin, or other drugs that have blood-thinning effects such as aspirin or NSAIDs
• antifungals, such as fluconazole, itraconazole, ketoconazole, or voriconazole
• cancer treatments, such as bosutinib, dabrafenib, dasatinib, erlotinib, neratinib, or pazopanib
• epilepsy medications, such as carbamazepine, fosphenytoin, phenobarbital, or phenytoin
• fentanyl
• hepatitis medications, such as boceprevir, ledipasvir, sofosbuvir, and telaprevir
• HIV medications (eg, atazanavir, indinavir, ritonavir, or saquinavir)
• iron supplements, such as ferrous fumarate, ferrous gluconate, or ferrous sulfate
• loperamide
• metformin
• multivitamins
• theophylline
• warfarin.

Note that this list is not all-inclusive and includes only common medications that may interact with famotidine. You should refer to the prescribing information for famotidine for a complete list of interactions.