Drug Guide

Generic Name

Famotidine

Brand Names Pepcid, Pepcid Preservative Free, Pepcid Preservative Free In Plastic Container, Pepcid Ac, Pepcid Rpd, Fluxid, Famotidine Preservative Free, Famotidine Preservative Free In Plastic Container, Famotidine Preservative Free (pharmacy Bulk)

Classification

Therapeutic: Gastrointestinal agent, Acid reducer

Pharmacological: Histamine-2 (H2) receptor antagonist

FDA Approved Indications

Gastroesophageal reflux disease (GERD)
Peptic ulcer disease (gastric and duodenal ulcers)
Erozive esophagitis
Pathologic hypersecretory conditions (e.g., Zollinger-Ellison syndrome)

Mechanism of Action

Famotidine selectively inhibits histamine at H2 receptors of gastric parietal cells, decreasing gastric acid secretion.

Dosage and Administration

Adult: Typically 20 mg once or twice daily; doses may vary based on condition and response.

Pediatric: Generally 0.5-1 mg/kg twice daily for children, but dose should be individualized and guided by a pediatrician.

Geriatric: Same as adult, but consider renal function and adjust dosage accordingly.

Renal Impairment: Dose adjustment recommended, usually to 20 mg once daily or less, depending on severity.

Hepatic Impairment: Use with caution; no specific dose adjustment recommended but monitor closely.

Pharmacokinetics

Absorption: Well absorbed, with peak plasma concentrations in 1-3 hours.

Distribution: Widely distributed, crosses the placenta, minimal protein binding.

Metabolism: Negligible hepatic metabolism.

Excretion: Primarily excreted unchanged in urine.

Half Life: 2.5-4 hours.

Contraindications

Hypersensitivity to famotidine or other H2 antagonists.

Precautions

Use with caution in renally impaired patients.
Monitor for GI infections due to reduced acidity.
Pregnancy Category B; consult healthcare provider before use during pregnancy.
Lactation: consider benefits vs. risks; famotidine passes into breast milk.

Adverse Reactions - Common

Headache (Uncommon)
Dizziness (Uncommon)
Constipation or diarrhea (Uncommon)

Adverse Reactions - Serious

CNS effects (confusion, agitation) particularly in elderly or renally impaired (Rare)
Cardiovascular reactions (arrhythmias) (Rare)
Allergic reactions (rash, anaphylaxis) (Rare)

Drug-Drug Interactions

Cimetidine (increases famotidine levels)

Drug-Food Interactions

No significant food interactions noted.

Drug-Herb Interactions

Use caution with herbs affecting gastric pH or cytochrome P450 enzymes.

Nursing Implications

Assessment: Monitor for relief of symptoms, assess for adverse reactions, and renal function.

Diagnoses:

Risk for GI infections related to decreased gastric acidity.
Impaired comfort related to GERD.

Implementation: Administer as prescribed, monitor renal function, educate on timing with meals and other meds.

Evaluation: Assess symptom relief and monitor for adverse effects.

Patient/Family Teaching

Take famotidine exactly as prescribed.
Report any signs of allergic reactions or CNS effects.
Do not crush or chew sustained-release formulations.
Notify healthcare provider if symptoms persist or worsen.

Special Considerations

Black Box Warnings:

No black box warnings for famotidine.

Genetic Factors: Limited data; genetic polymorphisms unlikely to significantly impact famotidine action.

Lab Test Interference: May interfere with assessment of urinary pH.

Overdose Management

Signs/Symptoms: Drowsiness, tachycardia, or mental status changes may occur.

Treatment: Supportive care; activated charcoal if ingestion is recent; hemodialysis in severe cases.

Storage and Handling

Storage: Store at room temperature, 20-25°C (68-77°F).

Stability: Stable for the duration of the labeled shelf life.