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Famotidine

Class: Histamine H2-Antagonists
VA Class: GA301
Chemical Name: 3-[[[2-[(Aminoiminomethyl)amino]-4-thiazolyl]methyl]thio]-N-(aminosulfonyl)propanimidamide
Molecular Formula: C8H15N7O2S3
CAS Number: 76824-35-6
Brands: Pepcid

Medically reviewed by Drugs.com on Jul 22, 2021. Written by ASHP.

Introduction

Histamine H2 receptor antagonist.

Uses for Famotidine

Duodenal Ulcer

Short-term treatment of active duodenal ulcer (endoscopically or radiographically confirmed).

Maintenance of healing and reduction in recurrence of duodenal ulcer.

Pathologic GI Hypersecretory Conditions

Treatment of Zollinger-Ellison syndrome, multiple endocrine adenomas.

Gastric Ulcer

Short-term treatment of active benign gastric ulcer.

Gastroesophageal Reflux (GERD)

Short-term treatment of symptomatic GERD.

Short-term treatment of esophagitis, including erosions or ulcers (endoscopically diagnosed) in patients with GERD.

Self-medication as initial therapy for less severe symptomatic GERD.

Short-term self-medication for relief of heartburn symptoms in adults and adolescents ≥12 years of age.

Short-term self-medication for prevention of heartburn symptoms associated with acid indigestion and sour stomach brought on by ingestion of certain foods and beverages in adults and children ≥12 years of age.

Famotidine Dosage and Administration

Administration

Administered orally, or by slow IV injection or intermittent IV infusion in hospitalized patients with pathological GI hypersecretory conditions or intractable duodenal ulcer, or when oral therapy is not feasible.

Oral Administration

Administer with or without food; administration with food may slightly enhance bioavailabilty.

Antacids may be used as necessary for pain relief.

Tablet for self-medication should be administered with a glass of water.

Chewable tablets (Pepcid AC Chewable, Pepcid Complete) for self-medication should be chewed thoroughly before swallowing.

For duodenal ulcer treatment, the advantage of administration once daily at bedtime (when convenience is important for compliance) over twice-daily administration has not been determined.

For gastric ulcer treatment in adults, administer once daily at bedtime.

For gastroesophageal reflux, once daily dosage not considered appropriate.

Oral Suspension

Add 46 mL of water to bottle containing 400 mg of famotidine for 40 mg/5mL suspension.

Shake oral suspension vigorously for 5–10 seconds after reconstitution and before each use.

Intermittent Direct IV Injection

Dilution

Dilute 20 mg to 5–10 mL with 0.9% sodium chloride injection or other compatible IV solution before direct IV injection.

Rate of Administration

Inject over not less than 2 minutes (no faster than 10 mg/minute).

Intermittent IV infusion

Dilution

Dilute 20 mg in at least 100 mL of 5% dextrose injection or other compatible IV solution.

No additional dilution required for commercially available infusion solution (20 mg famotidine in 50 mL of 0.9% sodium chloride injection).

Rate of Administration

Over 15–30 minutes.

Dosage

Pediatric Patients

General Parenteral Dosage

May administer IV in hospitalized pediatric patients with pathologic hypersecretory conditions, intractable ulcer, or for short-term use when oral therapy is not feasible.

Safety and efficacy have not been established in children <1 year of age.

Treatment of Children 1–16 Years of Age

Individualize duration and dosage based on clinical response and/or gastric or esophageal pH determination and endoscopy.

Intermittent Direct IV Injection

Initially, 0.25 mg/kg (15-minute infusion) every 12 hours (maximum 40 mg daily). Up to 0.5 mg/kg every 12 hours has provided gastric acid suppression.

Intermittent IV Infusion

Initially, 0.25 mg/kg (over not less than 2 minutes) every 12 hours (maximum 40 mg daily). Up to 0.5 mg/kg every 12 hours has provided gastric acid suppression

Gastroesophageal Reflux
Treatment of GERD in Infants <3 Months of Age
Oral

0.5 mg/kg once daily for up to 4 weeks.

Infants should also be receiving conservative measures (e.g., thickened feedings).

IV

Safety and efficacy not established.

Treatment of GERD in Infants 3 Months to <1 Year of Age
Oral

0.5 mg/kg twice daily for up to 4 weeks.

Infants should also be receiving conservative measures (e.g., thickened feedings).

IV

Safety and efficacy not established.

Treatment of GERD in Children 1–16 Years of Age
Oral

1 mg/kg daily in 2 divided doses (maximum 40 mg twice daily); up to 2 mg/kg daily has been used.

Individualize duration and dosage based on clinical response and/or gastric or esophageal pH determination and endoscopy.

IV

Dosage not established.

Treatment of Esophagitis in Children 1- 16 Years of Age
Oral

1 mg/kg daily in 2 divided doses (maximum 40 mg twice daily); up to 2 mg/kg daily has been used.

Individualize duration and dosage based on clinical response and/or gastric or esophageal pH determination and endoscopy.

IV

Dosage not established.

Self-medication for Heartburn in Adolescents ≥12 Years of Age
Oral

10-mg tablets: 10 mg once or twice daily (maximum 20 mg in 24 hours continuously for 2 weeks) or as directed by clinician.

Chewable tablets: 10 mg once or twice daily (maximum 20 mg in 24 hours continuously for 2 weeks) or as directed by clinician. Do not swallow whole; chew completely before swallowing.

20-mg tablets: 20 mg once or twice daily (maximum 40 mg in 24 hours continuously for 2 weeks) or as directed by clinician.

Fixed combination of famotidine, calcium carbonate, and magnesium hydroxide (Pepcid Complete): 1 tablet (10 mg of famotidine) once or twice daily (maximum 2 tablets in 24 hours continuously for 2 weeks). Do not swallow whole; chew completely before swallowing.

Self-medication for Prevention of Heartburn In Adolescents ≥12 Years of Age
Oral

10-mg tablets: 10 mg once or twice daily (15–60 minutes before ingestion of causative food or beverage); maximum 20 mg in 24 hours continuously for 2 weeks or as directed by clinician.

10-mg chewable tablets: 10 mg once or twice daily (15–60 minutes before ingestion of causative food or beverage); maximum 20 mg in 24 hours continuously for 2 weeks or as directed by clinician. Do not swallow whole; chew completely before swallowing.

20-mg tablets: 20 mg once or twice daily (10–60 minutes before ingestion of causative food or beverage); maximum 40 mg in 24 hours continuously for 2 weeks or as directed by clinician.

Duodenal Ulcer
Treatment of Duodenal Ulcer in Children 1–16 Years of Age
Oral

0.5 mg/kg once daily at bedtime or in 2 divided doses daily (maximum 40 mg daily); up to 1 mg/kg daily has been used.

Individualize duration and dosage based on clinical response and/or gastric or esophageal pH determination and endoscopy.

Gastric Ulcer
Treatment of Gastric Ulcer in Children 1–16 Years of Age
Oral

0.5 mg/kg once daily at bedtime or in 2 divided doses daily (maximum 40 mg daily); up to 1 mg/kg daily has been used.

Individualize duration and dosage based on clinical response and/or gastric or esophageal pH determination and endoscopy.

Adults

General Parenteral Dosage

May administer IV in hospitalized adults with pathologic hypersecretory conditions, intractable ulcer, or for short-term use when oral therapy is not feasible.

Dosage for parenteral administration in patients with GERD has not been established.

Intermittent Direct IV Injection

20 mg every 12 hours (maximum 40 mg daily).

Intermittent IV Infusion

20 mg every 12 hours (maximum 40 mg daily).

Gastroesophageal Reflux
Treatment of GERD
Oral

20 mg twice daily for up to 6 weeks.

40 mg once daily at bedtime also has been used, but is less effective and not considered appropriate therapy.

Treatment of Esophagitis
Oral

20 or 40 mg twice daily for up to 12 weeks.

Self-medication for Heartburn
Oral

10-mg tablets: 10 mg once or twice daily (maximum 20 mg in 24 hours continuously for 2 weeks) or as directed by clinician.

Chewable tablets: 10 mg once or twice daily (maximum 20 mg in 24 hours continuously for 2 weeks) or as directed by clinician. Do not swallow whole; chew completely before swallowing.

Fixed combination of famotidine, calcium carbonate, and magnesium hydroxide (Pepcid Complete): 1 tablet (10 mg of famotidine) once or twice daily (maximum 2 tablets in 24 hours continuously for 2 weeks). Do not swallow whole; chew completely before swallowing.

20-mg tablets: 20 mg once or twice daily (maximum 40 mg in 24 hours continuously for 2 weeks) or as directed by clinician.

Self-medication for Prevention of Heartburn
Oral

10-mg tablets: 10 mg once or twice daily (15–60 minutes before ingestion of causative food or beverage); maximum 20 mg in 24 hours continuously for 2 weeks or as directed by clinician.

Chewable tablets: 10 mg once or twice daily (15–60 minutes before ingestion of causative food or beverage); maximum 20 mg in 24 hours continuously for 2 weeks or as directed by clinician. Do not swallow whole; chew completely before swallowing.

20-mg tablets: 20 mg once or twice daily (10–60 minutes before ingestion of causative food or beverage); maximum 40 mg in 24 hours continuously for 2 weeks or as directed by clinician .

Duodenal Ulcer
Treatment of Active Duodenal Ulcer
Oral

40 mg once daily at bedtime, or 20 mg twice daily.

Healing may occur within 2 weeks in some, and within 4 weeks in most patients; some patients may benefit from an additional 4 weeks of therapy.

Occasionally may be necessary to continue full-dose therapy for >6–8 weeks.

Safety and efficacy of continuing full-dose therapy for >8 weeks have not been established.

Maintenance of Healing of Duodenal Ulcer
Oral

20 mg once daily at bedtime.

Gastric Ulcer
Oral

40 mg daily at bedtime for up to 8 weeks.

Complete healing of gastric ulcers usually occurs within 8 weeks.

Safety and efficacy of therapy for >8 weeks have not been established.

Pathologic GI Hypersecretory Conditions
Zollinger-Ellison Syndrome
Oral

20 mg every 6 hours. Higher doses administered more frequently may be necessary; adjust dosage according to response and tolerance and continue as long as necessary.

20–160 mg every 6 hours generally has been necessary to maintain basal gastric acid secretion at <10 mEq/hour.

Up to 160 mg every 6 hours, or 800 mg daily in divided doses, has been used in severe disease.

Intermittent IV Infusion

20 mg every 12 hours. Higher initial dosage may be required; adjust to individual needs and continue as long as necessary.

Prescribing Limits

Pediatric Patients

General Parenteral Dosage
Treatment of children 1–16 Years of Age
Intermittent Direct IV Injection

Maximum 40 mg daily.

Intermittent IV Infusion

Maximum 40 mg daily.

Gastroesophageal Reflux
Treatment of GERD in Infants <1 Year of Age
Oral

Safety and efficacy for >4 weeks not established.

Treatment of GERD without Esophagitis in Children 1–16 Years of Age
Oral

Maximum 40 mg twice daily.

Treatment of Esophagitis (including Erosions, Ulcerations) in Children 1- 16 Years of Age
Oral

Maximum 40 mg twice daily.

Self-Medication For Heartburn in Adolescents ≥12 Years of Age
Oral

Maximum 20 or 40 mg in 24 hours continuously for 2 weeks.

Self-medication for Prevention of Heartburn in Adolescents ≥12 Years of Age
Oral

Maximum 20 or 40 mg in 24 hours continuously for 2 weeks.

Duodenal Ulcer
Treatment of Active Duodenal Ulcer in Children 1–16 Years of Age
Oral

Maximum 40 mg daily.

Gastric Ulcer
Treatment of Gastric Ulcer in Children 1–16 Years of Age
Oral

Maximum 40 mg daily.

Adults

General Parenteral Dosage
Intermittent Direct IV Injection

Maximum 40 mg daily.

Intermittent IV Infusion

Maximum 40 mg daily.

Gastroesophageal Reflux
Treatment of Symptomatic GERD
Oral

Safety and efficacy for >6 weeks not established.

Treatment of Esophagitis
Oral

Safety and efficacy for >12 weeks not established.

Self-medication for Heartburn
Oral

Maximum 20 or 40 mg in 24 hours continuously for 2 weeks.

Self-medication for Prevention of Heartburn

Maximum 20 or 40 mg in 24 hours continuously for 2 weeks.

Duodenal Ulcer
Treatment of Active Duodenal Ulcer
Oral

Safety for >8 weeks not established.

Gastric Ulcer
Short-term Treatment of Active Benign Gastric Ulcer
Oral

Safety and efficacy for >8 weeks not established.

Pathologic GI Hypersecretory Conditions (e.g., Zollinger-Ellison Syndrome)
Oral

Up to 160 mg every 6 hours, or 800 mg daily in divided doses.

Special Populations

Renal Impairment

Pediatric Patients

Consider dosage adjustment in children with moderate or severe renal impairment.

Adults

In adults, modify dose and/or frequency of administration to the degree of renal impairment; adverse CNS effects have been reported.

Moderate (Clcr<50 mL/minute) or Severe (Clcr< 10 mL/minute)
Oral

Decrease to 50% of usual dosage.

Alternatively, increase dosing interval to 36–48 hours according to response.

IV

Decrease to 50% of usual dosage.

Alternatively, increase dosing interval to 36–48 hours according to response.

Clcr of 30–60 mL/minute per 1.48 m2

50% of usual adult dosage has been recommended.

Clcr < 30 mL/minute per 1.48 m2

25% of usual adult dosage has been recommended.

Cautions for Famotidine

Contraindications

  • Known hypersensitivity to famotidine, any ingredient in the formulation, or to other histamine H2 antagonists (i.e., cimetidine, nizatidine, ranitidine).

Warnings/Precautions

General Precautions

Gastric Malignancy

Response to famotidine does not preclude presence of gastric malignancy.

Phenylketonuria

Pepcid AC chewable tablets contain aspartame (Nutrasweet), which is metabolized in the GI tract to provide 1.4 mg of phenylalanine per tablet.

Respiratory Effects

Administration of H2-receptor antagonists has been associated with an increased risk for developing certain infections (e.g., community-acquired pneumonia).

Use of Fixed Combination

When used in fixed combination with other agents, consider the cautions, precautions, and contraindications associated with the concomitant agents.

Specific Populations

Pregnancy

Category B.

Self-medication in pregnant women: consult clinician before using.

Lactation

Distributed into milk. Discontinue nursing or the drug.

Self-medication in nursing women: consult clinician before using.

Pediatric Use

Infants <1 year of age: Consider for GERD treatment only if other conservative measures (e.g., thickened feedings) are used concurrently and potential benefits outweigh risks.

Safety and efficacy for self-medication not established in children <12 years of age; do not use unless directed by clinician.

Renal Impairment

Use with caution. Dosage adjustments necessary in patients with severe renal impairment. (See Renal Impairment under Dosage and Administration.)

Common Adverse Effects

Headache, dizziness, constipation, diarrhea.

Interactions for Famotidine

Does not appear to inhibit hepatic metabolism of drugs by hepatic CYP isoenzymes.

Antacids appear to cause slight but clinically unimportant decrease in bioavailability. May concomitantly administer with antacids.

Famotidine Pharmacokinetics

Absorption

Bioavailability

Oral: about 40–50%. Similar (50%) in children 11–15 years of age.

Tablets and oral suspension reportedly are bioequivalent.

Onset

Gastric acid inhibition within 1 hour after IV or oral administration. Peak inhibition within 0.5–3 hours following IV, 1–4 hours following oral administration.

Duration

Dose-dependent inhibition of gastric acid secretion.

Inhibition of basal and nocturnal secretion for 10–12 hours after single oral 20- or 40-mg dose.

Inhibition of food-stimulated secretion generally persists for 8–10 hours after morning administration, but may dissipate within 6–8 hours after a 20-mg oral dose in some patients.

Inhibition of nocturnal gastric acid secretion is 10–15 hours after single 10- or 20-mg IV dose.

Food

May slightly enhance bioavailability.

Distribution

Extent

Widely distributed, highest concentrations in the kidney, liver, pancreas, and submandibular gland.

Distributed into human milk.

Does not cross the placenta in animal studies; not known if famotidine crosses the placenta in humans.

Plasma Protein Binding

15–20%.

Elimination

Metabolism

Metabolized in the liver to inactive famotidine S-oxide (S-famotidine).

Minimal first-pass metabolism.

Elimination Route

Excreted principally in urine; 25–30% excreted unchanged within 24 hours after oral administration, 65–80% after IV administration. Small fraction of orally administered dose is excreted in urine as famotidine S-oxide. Remainder of orally administered dose eliminated in feces.

Interindividual variation in metabolism and excretion.

Half-life

2.5–4 hours (adults).

Special Populations

In patients with renal impairment, close correlation between Clcr and elimination half-life; >20 hours when Clcr <10 mL/minute, 24 hours in anuric patients.

Does not appear to be removed by hemodialysis.

Stability

Storage

Oral

Tablets

20 and 40 mg film-coated tablets: 25°C (may be exposed to 15–30°C) in tight, light-resistant containers.

Tablets for Self-medication

10 mg tablets, chewable tablets, film-coated tablets: 25–30°C.

10 mg chewable tablets in combination with calcium carbonate and magnesium hydroxide: 25–30°C.

20 mg film-coated tablets: 20–30°C.

Protect from moisture.

For Suspension

Reconstituted suspension or dry powder: 25°C (may be exposed to 15–30°C) in tight containers.

Suspension may be refrigerated; protect from freezing.

Discard unused suspension after 30 days.

Parenteral

Injection

2–8°C; expiration date of 24 months following the date of manufacture when stored at this temperature. If freezing occurs, thaw at room temperature, or in warm water bath, or under running hot tap water; allow sufficient time for dissolution of all ingredients. Do not thaw by microwave because of potential hazard of rapidly increased temperature and vapor pressure in a closed system. Diluted solutions of famotidine not used immediately after preparation should be refrigerated and used within 48 hours.

Injection for IV infusion only

25°C. Protect from excessive heat; brief exposure up to 35°C will not adversely affect the stability of the solution. Stable for 15 months when stored as recommended.

Compatibility

For information on systemic interactions resulting from concomitant use, see Interactions.

Parenteral

Solution CompatibilityHID

Compatible

Amino acids

Dextrose 5% in water

Fat emulsion 10%, IV

Sodium chloride 0.9%

Drug Compatibility
Admixture CompatibilityHID

Compatible

Cefazolin sodium

Flumazenil

Vancomycin HCl

Y-Site CompatibilityHID

Compatible

Acyclovir sodium

Allopurinol sodium

Amifostine

Aminophylline

Amiodarone HCl

Ampicillin sodium

Ampicillin sodium–sulbactam sodium

Amsacrine

Anakinra

Atropine sulfate

Aztreonam

Bivalirudin

Bretylium tosylate

Calcium gluconate

Cefazolin sodium

Cefotaxime sodium

Cefoxitin sodium

Ceftazidime

Ceftizoxime sodium

Ceftriaxone sodium

Cefuroxime sodium

Chlorpromazine HCl

Cisplatin

Cladribine

Cyclophosphamide

Cytarabine

Dexamethasone sodium phosphate

Dexmedetomidine HCl

Dextran 40

Digoxin

Diphenhydramine HCl

Dobutamine HCl

Docetaxel

Dopamine HCl

Doxorubicin HCl

Doxorubicin HCl liposome injection

Droperidol

Enalaprilat

Epinephrine HCl

Erythromycin lactobionate

Esmolol HCl

Etoposide phosphate

Fenoldopam mesylate

Filgrastim

Fluconazole

Fludarabine phosphate

Folic acid

Gemcitabine HCl

Gentamicin sulfate

Granisetron HCl

Haloperidol lactate

Heparin sodium

Hetastarch in lactated electrolyte injection (Hextend)

Hydrocortisone

Hydrocortisone sodium succinate

Hydromorphone HCl

Hydroxyzine HCl

Imipenem–cilastatin sodium

Inamrinone lactate

Isoproterenol HCl

Labetalol HCl

Lidocaine HCl

Linezolid

Lorazepam

Magnesium sulfate

Melphalan HCl

Meperidine HCl

Methotrexate sodium

Methylprednisolone sodium succinate

Metoclopramide HCl

Midazolam HCl

Morphine sulfate

Nafcillin sodium

Nicardipine HCl

Nitroglycerin

Norepinephrine bitartrate

Ondansetron HCl

Oxacillin sodium

Oxalipatin

Paclitaxel

Pemetrexed disodium

Perphenazine

Phenylephrine HCl

Phenytoin sodium

Phytonadione

Potassium chloride

Potassium phosphates

Procainamide HCl

Propofol

Remifentanil HCl

Sargramostim

Sodium bicarbonate

Sodium nitroprusside

Teniposide

Theophylline

Thiamine HCl

Thiotepa

Ticarcillin disodium–clavulanate potassium

Tirofiban HCl

Verapamil HCl

Vinorelbine tartrate

Incompatible

Amphotericin B cholesteryl sulfate complex

Azithromycin

Cefepime HCl

Lansoprazole

Piperacillin sodium–tazobactam sodium

Variable

Furosemide

Actions

  • Inhibits daytime, nocturnal basal and stimulated gastric acid secretion.

  • Competitively inhibits histamine at parietal cell H2 receptors.

Advice to Patients

  • Importance of following dosage instructions when famotidine is administered for self-medication, unless otherwise directed by a clinician.

  • Importance of promptly informing clinician of persistent abdominal pain or difficulty swallowing.

  • Importance of patients informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs; antacids (calcium carbonate and magnesium hydroxide) in Pepcid Complete may interact with other drugs.

  • Importance of women informing clinician if they are or plan to become pregnant or plan to breast-feed.

  • Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Famotidine

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

For suspension

40 mg/5 mL

Pepcid (with parabens)

Merck

Tablets

10 mg

Pepcid AC Gelcaps

J&J-Merck

Tablets, chewable

10 mg

Pepcid AC (with aspartame)

J&J-Merck

Tablets, film-coated

10 mg

Pepcid AC

J&J-Merck

20 mg*

Pepcid

Merck

Pepcid AC Maximum Strength

J&J-Merck

40 mg

Pepcid

Merck

Parenteral

For injection, concentrate

10 mg/mL (pharmacy bulk package)

Famotidine for Injection

Bedford

For injection concentrate, for IV use

10 mg/mL

Famotidine for Injection

American Pharmaceutical Partners, Baxter, Bedford

Pepcid I.V. (preservative-free; in single-dose vials or with benzyl alcohol 0.9% in multiple-dose vials)

Merck

Famotidine in Sodium Chloride

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Parenteral

Injection, for IV use only

0.4 mg/mL (20 mg) in 0.9% Sodium Chloride

Pepcid Premixed in Iso-osmotic Sodium Chloride Injection (Galaxy [Baxter])

Merck

Famotidine Combinations

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Tablets, chewable

10 mg with calcium carbonate 800 mg and magnesium hydroxide 165 mg

Pepcid Complete

J&J-Merck

AHFS DI Essentials™. © Copyright 2022, Selected Revisions August 1, 2007. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

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