Famosic

Approved Indications:

• Gastroesophageal Reflux Disease (GERD):
• Treatment of symptomatic GERD.
• Healing and maintenance of erosive esophagitis associated with GERD.
• Peptic Ulcer Disease:
• Duodenal Ulcer: Short-term treatment (4–8 weeks); and maintenance therapy to prevent recurrence.
• Benign Gastric Ulcer: Short-term treatment (up to 8 weeks).
• Pathological Hypersecretory Conditions:
• Zollinger-Ellison Syndrome.
• Multiple Endocrine Adenomas.
• Systemic Mastocytosis.
• Over-the-Counter (OTC) Use:
• Prevention and relief of occasional heartburn due to acid indigestion, especially associated with food and beverages.

Clinically Accepted Off-label Uses:

• Stress Ulcer Prophylaxis: In critically ill or mechanically ventilated patients.
• Eosinophilic Esophagitis (EoE): Used as adjunct acid suppression therapy.
• Chronic Idiopathic Urticaria or Mastocytosis: Used alongside H1-antihistamines for enhanced symptom control.
• Non-ulcer Dyspepsia: Especially in patients intolerant to PPIs or when rapid symptom relief is needed.

Route of Administration: Oral or Intravenous (IV)
Frequency: Once or twice daily depending on indication
Dose Adjustment: Required in renal impairment

Adults:

• Duodenal Ulcer (Acute): 40 mg orally once daily at bedtime or 20 mg twice daily for 4–8 weeks.
• Duodenal Ulcer (Maintenance): 20 mg orally once daily at bedtime.
• Benign Gastric Ulcer: 40 mg orally once daily at bedtime for up to 8 weeks.
• GERD (Symptomatic): 20 mg orally twice daily for up to 6 weeks.
• Erosive Esophagitis: 20–40 mg orally twice daily for 6–12 weeks.
• Zollinger-Ellison Syndrome: Start with 20 mg IV or orally every 6 hours; adjust to individual response, up to 160 mg every 6 hours.
• OTC Heartburn Relief: 10 to 20 mg orally once or twice daily before meals, not exceeding 40 mg/day.

Pediatrics (1–16 years):

• GERD or Ulcers: 0.5 mg/kg orally twice daily (maximum: 40 mg/day).
• IV: 0.25–0.5 mg/kg every 12 hours.

Infants (<1 year):

• GERD:
  • <3 months: 0.5 mg/kg once daily
  • 3 months to 1 year: 0.5 mg/kg twice daily

Geriatric Patients:

• Use with caution due to increased sensitivity.
• Renal function should be monitored.

Renal Impairment (CrCl <50 mL/min):

• Reduce dose by 50% or extend dosing interval to every 36–48 hours.

IV Administration:

• Intermittent Bolus: 20 mg IV every 12 hours over at least 2 minutes.
• Continuous Infusion: 20–160 mg over 24 hours, based on condition severity.

Famotidine is a potent histamine H2-receptor antagonist that selectively and competitively inhibits the action of histamine at H2 receptors located on gastric parietal cells. This results in decreased basal, nocturnal, and stimulated gastric acid secretion, both in volume and hydrogen ion concentration. By blocking histamine-induced activation of adenylate cyclase and subsequent cAMP formation, famotidine reduces the activity of the proton pump indirectly, thereby alleviating symptoms of acid reflux and promoting the healing of acid-related mucosal injuries.

• Absorption: Well absorbed orally; peak plasma concentration occurs within 1–3 hours.
• Bioavailability: 40–45%; unaffected significantly by food.
• Distribution: Low protein binding (~15–20%); widely distributed in body fluids.
• Metabolism: Minimal hepatic metabolism (~10–20%); minor CYP involvement.
• Elimination: Primarily renal; ~65–70% excreted unchanged in urine.
• Half-life: 2.5 to 3.5 hours in healthy adults; prolonged in renal dysfunction.
• Onset of Action: Within 1 hour orally; faster with IV.
• Duration of Action: 10 to 12 hours after oral administration.

Pregnancy:

• Category B (FDA legacy classification):
  Animal studies have not demonstrated fetal harm; however, no well-controlled studies exist in pregnant women.
  Use only if clearly necessary.

Lactation:

• Famotidine is excreted in breast milk in small amounts.
• No harmful effects reported in breastfed infants.
• Short-term use considered acceptable.
• Use with caution in prolonged therapy; consider monitoring infant or choosing an alternative.

• Primary Class: H2-Receptor Antagonist (H2 Blocker)
• Subclass: Second-generation H2-blocker
• Form Availability: Oral tablets, oral suspension, intravenous injection
• OTC Availability: Low-dose strengths (10 mg, 20 mg)

• Hypersensitivity to famotidine or other H2-receptor antagonists.
• History of serious hypersensitivity (e.g., anaphylaxis, angioedema) to the drug.
• Patients with known acute porphyria.
• Severe renal impairment without appropriate dose adjustment.

• Renal Impairment: Increased risk of CNS adverse effects (e.g., confusion, seizures); dosage adjustment is necessary.
• CNS Effects: Confusion, hallucinations, or seizures can occur, particularly in elderly or renal-impaired patients.
• Vitamin B12 Deficiency: Prolonged acid suppression may reduce B12 absorption.
• QT Prolongation: Rare; primarily in patients with renal dysfunction or when used in high IV doses.
• Masking of Malignancy: Symptom relief may delay diagnosis of gastric malignancy; further evaluation is warranted in atypical or persistent symptoms.
• Pediatric Use: Safety established in children ≥1 year for short-term use.

Common (≥1%):

• Gastrointestinal: Constipation, diarrhea, nausea
• Neurological: Headache, dizziness
• General: Fatigue

Uncommon to Rare:

• CNS: Confusion, hallucinations, agitation (especially in elderly or renal-impaired)
• Dermatologic: Rash, pruritus, urticaria
• Hematologic: Thrombocytopenia (rare but serious)
• Cardiac: QT prolongation (rare, IV use)
• Hepatic: Transient liver enzyme elevations

Severity and Onset:

• Most adverse events are mild to moderate and transient.
• CNS effects often appear within a few days in high-risk patients.

• Reduced Absorption of pH-dependent Drugs:
• Ketoconazole, Itraconazole, Atazanavir – Decreased efficacy due to reduced gastric acidity.
• Dasatinib: Concomitant use should be avoided.
• Probenecid: May increase famotidine levels by reducing renal excretion.
• No Major CYP450 Interactions:
  Famotidine does not significantly inhibit or induce CYP enzymes, reducing the likelihood of metabolic drug interactions.

Food & Alcohol:

• No significant interaction with food.
• Alcohol may worsen underlying acid reflux symptoms but does not interact directly.

• FDA (2020–2023):
  Famotidine replaced ranitidine as the preferred H2-blocker after the withdrawal of ranitidine from the market.
• GERD Treatment Guidelines (ACG 2022):
  Famotidine recognized as a safer alternative to PPIs in specific populations (e.g., elderly, pregnancy).
• COVID-19 Context:
  Studied in clinical trials as a potential adjunct treatment; no official indication approved.
• Ongoing Evaluation:
  Long-term acid suppression still being evaluated for effects on micronutrient absorption (B12, calcium).

Tablets:

• Store at 20°C to 25°C (68°F to 77°F)
• Allowable range: 15°C to 30°C (59°F to 86°F)
• Protect from moisture and excessive heat
• Keep container tightly closed

Oral Suspension (Reconstituted):

• Store at 2°C to 8°C (36°F to 46°F)
• Discard after 30 days
• Do not freeze

IV Formulation:

• Store vials at 20°C to 25°C
• Protect from light
• After dilution, stable at room temperature for 48 hours, or 7 days if refrigerated
• Do not use if solution is discolored or contains particulates