What Is Famotidine and How Does It Work?

Famotidine is a prescription and over the counter drug used to treat ulcers of the stomach and intestines and to prevent intestinal ulcers from coming back after they have healed. Famotidine is also used to treat certain stomach and throat problems such as erosive esophagitis, gastroesophageal reflux disease or GERD, and Zollinger-Ellison syndrome. It works by decreasing the amount of acid your stomach makes. It relieves symptoms such as cough that doesn’t go away, stomach pain, heartburn, and difficulty swallowing.  Famotidine belongs to a class of drugs known as H2 blockers. 

Famotidine is available under the following different brand names: Pepcid, Zantac 360, Act, Dyspep HB, Fluxid, and Acid Controller.

Dosages of Famotidine

Adult and pediatric dosages:

Injectable solution

  • 10 mg/ml
  • 0.4 mg/ml

Oral suspension

  • 40 mg/5 ml


  • 10 mg
  • 20 mg

Dosage Considerations – Should be Given as Follows:

Duodenal Ulcer

  • Acute treatment: 20 mg orally or intravenously every 12 hours or 40 mg orally at bedtime for 4-8 weeks
  • Maintenance: 20 mg orally at bedtime

Benign Gastric Ulcer

  • 40 mg orally at bedtime

Gastroesophageal Reflux Disease


  • 20 mg orally every 12 hours for 6 weeks
  • With esophagitis: 20-40 mg orally every 12 hours for up to 12 weeks


  • Children under 3 months: 0.5 mg/kg orally once daily for up to 8 weeks
  • Children 3-12 months: 0.5 mg/kg orally every 12 hours for up to 8 weeks
  • Children 1-16 years: 1 mg/kg/day orally divided every 12 hours; individual dose not to exceed 40 mg

Hypersecretory Conditions

  • 20 mg orally or intravenously every 6 hours, may increase up to 160 mg every 6 hours



  • 10-20 mg every 12 hours, it may take 15-60 min before eating foods that could cause heartburn


  • Children under 12 years: Not established
  • Children 12 years or older: 10-20 mg every 12 hours, may take 15-60 min before eating foods that could cause heartburn

Dosing Modifications

  • Creatinine clearance less than 50 mL/min: Give 50% of usual dose, or prolong dosing interval to q36-48hr
  • Peptic Ulcer, Pediatric
  • 1-16 years: 0.25 mg/kg intravenously every 12 hours or 0.5 mg/kg orally at bedtime; not to exceed 40 mg/day

What Are Side Effects Associated with Using Famotidine?

Common side effects include:

  • headache
  • diarrhea
  • dizziness
  • constipation

Other possible side effects of Famotidine include:

Body as a whole:

  • fever
  • weakness or lack of energy
  • fatigue


  • Irregular heartbeat (arrhythmia)
  • heart block (AV block)
  • palpitation
  • prolonged QT interval in patients with impaired renal function (rare)


  • changes in liver function (cholesteric jaundice)
  • hepatitis
  • liver enzyme abnormalities
  • vomiting
  • nausea
  • abdominal discomfort
  • loss of appetite
  • dry mouth


  • lowered white blood cells (rare)
  • reduction of white and red blood cells
  • reduction of white blood cells
  • deficiency of platelets


  • acute allergic reaction
  • rapid swelling
  • orbital or facial swelling
  • hives
  • rash
  • conjunctival injection


  • inflammation of muscle tissue
  • musculoskeletal pain including muscle cramps
  • joint pain

Nervous system/psychiatric:



Special senses:

Rare cases of impotence and rare cases of swelling of breast tissue in men.

This document does not contain all possible side effects and others may occur. Check with your doctor or other medical professional for additional information about side effects or other concerns about conditions related to your health.

What Other Drugs Interact with Famotidine?

If your doctor has directed you to use this NSAID, your medical doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first for more health information.

Famotidine has no known severe interactions with any drugs.

Serious Interactions of Famotidine include:

Mild Interactions of Famotidine include:

This information does not contain all possible interactions. Therefore, before using this drug, tell your doctor or pharmacist of all the medications you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions, concerns, or more health information.

What Are Warnings and Precautions for Famotidine?


  • This medication contains famotidine Do not take Pepcid, Act, Dyspep HB, Fluxid, or Acid Controller if you are allergic to famotidine or any ingredients contained in this drug
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Hypersensitivity to famotidine or other H2-receptor antagonists.

Effects of Drug Abuse

  • None

Short-Term Effects

  • See "What Are Side Effects Associated with Using Famotidine?”

Long-Term Effects

  • Increased risk of GI ulcers with prolonged use.
  • See "What Are Side Effects Associated with Using Famotidine?”


  • Use caution in patients with renal impairment; dosage adjustment recommended in moderate to severe renal impairment (Creatinine clearance less than 50 mL/min)
  • Prolonged QT interval reported (rare) in patients with renal impairment whose dose or dosing interval may not have been adjusted appropriately
  • Central nervous system adverse effects reported with moderate-to-severe renal impairment
  • Relief of symptoms does not eliminate the presence of gastric malignancy
  • State of confusion reported with use; risk increased in patients over 50 years of age and/or kidney or liver impairment
  • Prolonged treatment (over 2 years) may lead to vitamin B12 malabsorption, which can result in vitamin B12 deficiency; magnitude of deficiency is dose related; occurs most frequently in females and those younger than 30 years
  • Patients should not use over-the-counter (OTC) if difficulty swallowing, vomiting blood, and/or have bloody or black stools
  • Not for over-the-counter (OTC) use with other acid reducers

Pregnancy and Lactation

  • Famotidine use in pregnancy may be acceptable. Either animal studies show no risk but human studies are not available, or animal studies showed minor risks and human studies were done and showed no risk
  • Famotidine enters breast milk; use is not recommended when lactating
Medscape. Famotidine.

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