pharmacopeia
GET
/api/v1/drug/famotidine
2D structure
3-[[2-(diaminomethylideneamino)-1,3-thiazol-4-yl]methylsulfanyl]-N'-sulfamoylpropanimidamide
SMILES C1=C(N=C(S1)N=C(N)N)CSCC/C(=N/S(=O)(=O)N)/N
InChIKey XUFQPHANEAPEMJ-UHFFFAOYSA-N

Mechanism of action

Sourced from openFDA

Famotidine is a competitive inhibitor of histamine-2 (H 2 ) receptors. The primary clinically important pharmacologic activity of famotidine is inhibition of gastric secretion.

Histamine H2 Receptor

Indications

Sourced from openFDA
  • Famotidine tablets are indicated in adult and pediatric patients 40 kg and greater for the treatment of: • active duodenal ulcer (DU). • active gastric ulcer (GU).ICD-10: K25.9, K26.9

Contraindications

Sourced from openFDA
  • Famotidine tablets are contraindicated in patients with a history of serious hypersensitivity reactions (e.g., anaphylaxis) to famotidine or other histamine-2 (H 2 ) receptor antagonists. History of serious hypersensitivity reactions (e.g., anaphylaxis) to famotidine or other H 2 receptor antagonists.contraindicated

Dosage & administration

Sourced from openFDA

Indication Recommended Dosage ( 2.1 ) Adult and Pediatric Patients 40 kg and greater Active DU 40 mg once daily; or 20 mg twice daily Active Gastric Ulcer 40 mg once daily GERD 20 mg twice daily Erosive Esophagitis 20 mg twice daily; or 40 mg twice daily Adults Pathological Hypersecretory Conditions 20 mg every 6 hours; adjust to patient needs; maximum 160 mg every 6 hours Risk Reduction of DU Recurrence 20 mg once daily • See full prescribing information for complete dosing information, including dosing in renal impairment, and recommended treatment duration. ( 2.1 , 2.2 ) Administration ( 2.3 ): • Take once daily before bedtime or twice daily in the morning and before bedtime with or without food. 2.1 Recommended Dosage Table 1 shows the recommended dosage of famotidine 20 mg and 40 mg tablets in adult and pediatric patients weighing 40 kg and greater with normal renal function. The use of famotidine 20 mg and 40 mg tablets is not recommended in pediatric patients weighing less than 40 kg because the lowest available strength (20 mg) exceeds the recommended dose for these patients. Use another famotidine formulation for pediatric patients weighing less than 40 kg.

Warnings & precautions

Sourced from openFDA

• Central Nervous System (CNS) Adverse Reactions: Elderly patients and patients with renal impairment at increased risk; reduce the dosage. ( 2.2 , 5.1 , 8.5 , 8.6 ) • GI Malignancy: Absence of GI symptoms does not preclude the presence of gastric malignancy; evaluate prior to initiating therapy. ( 5.2 ) 5.1 Central Nervous System Adverse Reactions Central nervous system (CNS) adverse reactions, including confusion, delirium, hallucinations, disorientation, agitation, seizures, and lethargy, have been reported in elderly patients and patients with moderate and severe renal impairment treated with famotidine. Since famotidine blood levels are higher in patients with renal impairment than in patients with normal renal function, dosage adjustments are recommended in patients with renal impairment [see Dosage and Administration ( 2.2 ), Clinical Pharmacology ( 12.3 )]. 5.2 Concurrent Gastric Malignancy In adults, symptomatic response to therapy with famotidine does not preclude the presence of gastric malignancy. Consider evaluation for gastric malignancy in adult patients who have a suboptimal response or an early symptomatic relapse after completing treatment with famotidine.

Adverse reactions

Sourced from openFDA

The most common adverse reactions are: headache, dizziness, constipation, and diarrhea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Annora Pharma Private Limited at 1-866-495-1995 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trial Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Famotidine was studied in 7 US and international placebo- and active-controlled trials in approximately 2500 patients [see Clinical Studies ( 14 )]. A total of 1442 patients were treated with famotidine, including 302 treated with 40 mg twice daily, 456 treated with 20 mg twice daily, 461 treated with 40 mg once daily, and 396 treated with 20 mg once daily. The population was 17 to 91 years old, fairly well distributed between gender and race; however, the predominant race treated was Caucasian. The following adverse reactions occurred in greater than or equal to 1% of famotidine-treated patients: headache, dizziness and constipation.

Use in specific populations

Sourced from openFDA

• Geriatric Use: Use the lowest effective dose for an elderly patient and monitor renal function. ( 2.2 , 5.1 , 8.5 ) • Renal Impairment: Risk of CNS adverse reactions and QT prolongation in patients with moderate and severe renal impairment; reduce the dosage. ( 2.2 , 8.6 ) 8.1 Pregnancy Risk Summary Available data with H 2 -receptor antagonists, including famotidine, in pregnant women are insufficient to establish a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. In animal reproduction studies, no adverse development effects were observed with oral administration of famotidine at doses up to approximately 243 and 122 times, respectively, the recommended human dose of 80 mg per day for the treatment of erosive esophagitis (see Data). The estimated background risk for major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Pharmacokinetics

Sourced from openFDA
Metabolism
Absorption Famotidine is incompletely absorbed. The bioavailability of oral doses is 40 to 45%.

Overdosage

Sourced from openFDA

The types of adverse reactions in overdosage of famotidine are similar to the adverse reactions encountered with use of recommended dosages [see Adverse Reactions ( 6.1 )]. In the event of overdosage, treatment should be symptomatic and supportive. Unabsorbed material should be removed from the gastrointestinal tract, the patient should be monitored, and supportive therapy should be employed. Due to low binding to plasma proteins, famotidine is eliminated by hemodialysis. There is limited experience on the usefulness of hemodialysis as a treatment for famotidine overdosage.

Approval history

Sourced from openFDA
  • Apr 28, 1995NDANDA020325Kenvue Brands
  • Oct 16, 2000NDANDA020958Kenvue Brands
  • Apr 16, 2001ANDAANDA075622Sagent
  • Apr 16, 2001ANDAANDA075709Fresenius Kabi Usa
  • Apr 16, 2001ANDAANDA075718Dr Reddys Labs Ltd
  • Apr 16, 2001ANDAANDA075651Sagent
  • Apr 16, 2001ANDAANDA075488Hikma
  • Jul 16, 2025NDANDA219935Sagent

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
115,343 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Nausea7,6196.6%
  2. 2Fatigue7,1416.2%
  3. 3Diarrhoea6,7915.9%
  4. 4Chronic Kidney Disease6,7875.9%
  5. 5Drug Ineffective6,6315.7%
  6. 6Off Label Use5,5304.8%
  7. 7Dyspnoea5,4464.7%
  8. 8Headache5,1854.5%
  9. 9Pain4,7774.1%
  10. 10Acute Kidney Injury4,7674.1%
  11. 11Vomiting4,6634.0%
  12. 12Dizziness4,4423.9%
  13. 13Renal Failure4,1653.6%
  14. 14Death3,8153.3%
  15. 15Pneumonia3,6093.1%

Literature

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Recent PubMed references pinned to Famotidine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 10 most recently updated of 157 ClinicalTrials.gov registrations naming Famotidine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Famotidine work?
Famotidine is a competitive inhibitor of histamine-2 (H 2 ) receptors. The primary clinically important pharmacologic activity of famotidine is inhibition of gastric secretion.
What is Famotidine used for?
According to FDA labeling, Famotidine carries indications including: Famotidine tablets are indicated in adult and pediatric patients 40 kg and greater for the treatment of: • active duodenal ulcer (DU). • active gastric ulcer (GU).. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Famotidine?
Famotidine is classified as H2-receptor antagonists, Histamine-2 Receptor Antagonist, Histamine H2 Receptor Antagonists, Decreased Histamine Activity, Inhibition Gastric Acid Secretion.
What are the brand names for Famotidine?
Famotidine is marketed under brand names including Calmicid, Duexis, Duo Fusion, Pepcid, Pepcid Complete, Tums Dual Action, Zantac Reformulated Aug 2022.
What are the contraindications for Famotidine?
Famotidine labeling lists contraindications including: Famotidine tablets are contraindicated in patients with a history of serious hypersensitivity reactions (e.g., anaphylaxis) to famotidine or other histamine-2 (H 2 ) receptor antagonists. History of serious hypersensitivity reactions (e.g., anaphylaxis) to famotidine or other H 2 receptor antagonists.. Always consult the full prescribing information and a clinician.
Note. Data for famotidine is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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