Table of Contents

Famotidine (Injectable) — Comprehensive Medical Overview

Introduction

Famotidine is a potent histamine H2 receptor antagonist widely used to reduce gastric acid secretion. The injectable formulation allows rapid delivery and onset, primarily indicated in hospital settings for acute conditions requiring immediate acid suppression. Famotidine injection is commonly used to treat gastroesophageal reflux disease (GERD), peptic ulcers, Zollinger-Ellison syndrome, and stress ulcer prophylaxis in critically ill patients.

This article provides a thorough overview of injectable famotidine, detailing its uses, mechanism of action, dosage guidelines, side effects, warnings, drug interactions, and patient information.

Uses & Indications

Famotidine injectable is indicated for:

Treatment of active duodenal ulcers: To accelerate healing by reducing gastric acidity.
Gastroesophageal reflux disease (GERD): Managing erosive esophagitis and symptomatic relief.
Zollinger-Ellison syndrome: Reducing gastric acid hypersecretion due to gastrinomas.
Stress ulcer prophylaxis: Prevention of gastrointestinal bleeding in critically ill patients.
Pathologic hypersecretory conditions: Including multiple endocrine neoplasia.

The injectable form is preferred in patients unable to tolerate oral administration or requiring rapid acid suppression in acute settings.

How It Works

Famotidine is a selective antagonist of histamine H2 receptors located on gastric parietal cells. By blocking H2 receptors, famotidine:

Inhibits gastric acid secretion: Both basal and stimulated secretion are suppressed, leading to increased gastric pH.
Reduces volume and acidity of gastric secretions: This creates an environment conducive to ulcer healing and symptom relief.
Decreases pepsin secretion: Contributing to mucosal protection.

Unlike proton pump inhibitors (PPIs), famotidine works rapidly and is reversible, making it suitable for acute management.

Dosage and Administration

Formulations:

Famotidine injectable is supplied as a sterile solution for intravenous (IV) or intramuscular (IM) administration.

Recommended Dosage:

Duodenal ulcers: 20 mg IV or IM twice daily for 6-8 weeks.
GERD/esophagitis: 20 mg IV or IM twice daily, duration based on clinical response.
Zollinger-Ellison syndrome: Initial 20 mg IV or IM every 6 hours; dose adjusted according to gastric acid output.
Stress ulcer prophylaxis: 20 mg IV once daily, typically for the duration of ICU stay or risk period.

Administration Instructions:

IV injections should be administered slowly over 2 minutes to minimize injection site reactions.
IM injections should be deep into the gluteal or thigh muscles.
Dose adjustments may be necessary for renal impairment.

Pharmacokinetics

Absorption: Complete bioavailability with IM and IV routes.
Distribution: Widely distributed with low protein binding (~15-20%).
Metabolism: Minimal hepatic metabolism.
Elimination: Primarily excreted unchanged by the kidneys; half-life approximately 2.5-3.5 hours.
Dose adjustments: Required in patients with renal impairment to avoid accumulation.

Side Effects

Common Side Effects:

Headache.
Dizziness or fatigue.
Diarrhea or constipation.
Injection site pain or phlebitis.

Serious but Rare Side Effects:

Arrhythmias (particularly in patients with underlying heart conditions).
Confusion or agitation, especially in elderly or renally impaired patients.
Allergic reactions including rash, urticaria, or anaphylaxis.
Thrombocytopenia or neutropenia (rare hematologic effects).

Warnings and Precautions

Use with caution in patients with renal impairment; dose adjustment is essential.
Monitor elderly patients closely due to increased risk of CNS side effects.
Avoid rapid IV bolus to reduce risk of bradycardia or hypotension.
Hypersensitivity to famotidine or other H2 blockers contraindicates use.
Use caution in patients with phenylketonuria if product contains preservatives with phenylalanine.

Drug Interactions

Famotidine may reduce the absorption of drugs requiring an acidic environment (e.g., ketoconazole, atazanavir).
Concomitant use with other acid suppressants may increase risk of adverse effects.
Minimal cytochrome P450 interactions, making it relatively safe with most drugs.
Antacids may reduce absorption if administered simultaneously; stagger dosing.

Clinical Evidence and Benefits

Famotidine injection provides rapid symptom relief in acute peptic ulcer disease and GERD.
Effective in stress ulcer prophylaxis, reducing ICU patient morbidity.
Comparable efficacy to other H2 blockers and PPIs for many indications with a favorable safety profile.
Useful in settings where oral administration is not feasible, such as post-operative or critically ill patients.

Patient Counseling

Inform patients or caregivers about the purpose of famotidine injection and expected benefits.
Explain potential side effects and instruct to report severe reactions immediately.
Emphasize importance of adhering to dosing schedules and follow-up appointments.
Advise patients to avoid self-medication with over-the-counter acid suppressants unless directed.

FAQs

Q1: How fast does injectable famotidine work?
A: Relief can begin within an hour after administration.

Q2: Can famotidine injection be given with other medications?
A: Generally yes, but inform your healthcare provider about all medications to avoid interactions.

Q3: Is famotidine safe in pregnancy?
A: Famotidine is pregnancy category B and may be used if benefits outweigh risks; consult your doctor.

Q4: What if I miss a dose?
A: Administer as soon as possible unless close to the next dose; do not double dose.

Q5: Can I switch from injectable to oral famotidine?
A: Yes, transition is common once oral administration is feasible.

Summary

Famotidine injectable is an effective H2 receptor antagonist providing rapid gastric acid suppression in various acid-related disorders. Its safety and efficacy have been well-established in acute care settings, making it a valuable tool in the management of peptic ulcer disease, GERD, Zollinger-Ellison syndrome, and stress ulcer prophylaxis. Appropriate dosing, monitoring, and awareness of side effects ensure optimal therapeutic outcomes.

References

FDA Famotidine Injection Prescribing Information. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/019984s036lbl.pdf
Katz PO, Gerson LB, Vela MF. Guidelines for the diagnosis and management of gastroesophageal reflux disease. Am J Gastroenterol. 2013;108(3):308-328.
MedlinePlus. Famotidine Injection. https://medlineplus.gov/druginfo/meds/a682598.html
Brunton LL, et al. Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 13th Edition.
Mayo Clinic. Famotidine Uses and Side Effects. https://www.mayoclinic.org/drugs-supplements/famotidine-intravenous-route/description/drg-20066732