Famotidine

Trade Names:
Famotidine
- Injection 10 mg/mL
- Injection, pre-mixed 20 mg/50 mL in 0.9% NaCl

Trade Names:
Pepcid
- Tablets 20 mg
- Tablets 40 mg
- Powder for Oral Suspension 40 mg/5 mL when reconstituted

Trade Names:
Pepcid AC
- Tablets, chewable 10 mg
- Tablets 10 mg
- Gelcaps 10 mg

Trade Names:
Pepcid AC EZ Chews
- Tablets, chewable 20 mg

Trade Names:
Pepcid AC Maximum Strength
- Tablets 20 mg

Trade Names:
Pepcid RPD
- Tablets 20 mg
- Tablets 40 mg

Pharmacology

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Competitively blocks histamine at H ₂ receptors, particularly those in gastric parietal cells, leading to inhibition of gastric acid secretion.

Pharmacokinetics

Absorption

Bioavailability is 40% to 45%. T _max is 1 to 3 h (PO).

Distribution

Protein binding is 15% to 20% and Vd is 1.1 to 1.4 L/kg.

Metabolism

The only identified metabolite is S-oxide.

Elimination

The t _{1/ 2} is 2.5 to 3.5 h and 25% to 30% of the oral dose and 65% to 70% of the IV dose is excreted unchanged in the urine.

Onset

PO Within 1 h.

Peak

IV Within 30 min. PO 1 to 3 h.

Duration

IV / PO 10 to 12 h.

Special Populations

The t _½ is increased.

Indications and Usage

Short-term treatment of active duodenal ulcer; maintenance therapy for duodenal ulcer patients at reduced dosage after healing of an active ulcer; short-term treatment of active benign gastric ulcer; short-term treatment of gastroesophageal reflux disease (GERD, including erosive or ulcerative disease diagnosed by endoscopy); treatment of pathological hypersecretory conditions. IV is indicated in some hospitalized patients with pathologic hypersecretory conditions, intractable ulcers, or patients unable to take PO.

Relief and prevention of symptoms of heartburn, acid indigestion, and sour stomach.

Contraindications

Hypersensitivity to other H ₂ antagonists.

Dosage and Administration

PO 40 mg at bedtime or 20 mg twice daily for 4 to 8 wk.

20 mg at bedtime.

PO 0.5 mg/kg/day at bedtime or divided twice daily (max, 40 mg/day).

PO 40 mg at bedtime.

PO 20 mg twice daily for up to 6 wk.

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

PO 0.5 mg/kg once daily for up to 8 wk.

PO 0.5 mg/kg twice daily for up to 8 wk.

PO 1 mg/kg/day divided twice daily (max, 40 mg twice daily).

PO Start at 20 mg every 6 h; adjust to individual patient needs and continue as long as clinically indicated; doses up to 160 mg every 6 h have been used.

May need to reduce dose 50%, or increase dosing interval to 36 to 46 h.

Parenteral use in GERD not established.

IV 20 mg every 12 h.

IV 0.25 mg/kg (injected over a period of no less than 2 min or as 15-min infusion) every 12 h (max 40 mg/day).

1 tablet.

1 tablet 10 to 60 min before eating or drinking.

2 tablets/24 h.

General Advice

• Oral
• Tablets and suspension are bioequivalent.
• Administer without regard to meals or antacids.
• Prepare suspension at time of dispensing. Add 46 mL purified water.
• Shake suspension vigorously for 5 to 10 sec immediately after adding the water and immediately before measuring dose. Use dosing syringe, dosing spoon, or dosing cup to measure and administer dose.

• Injection
• For IV administration only.
• Do not add supplementary medication.
• Do not use if discolored, cloudy, or contains particulate matter.
• Check premixed injection container for leaks by firmly squeezing container. Do not use if leaks detected or if seal is broken.
• Do not use premixed containers in series connections to avoid air embolism.
• Injection solution (10 mg/mL) is compatible with water for injection, sodium chloride 0.9%, dextrose 5% and 10% injection, lactated Ringer's injection.
• Injection solution diluted with compatible fluids should be used immediately or refrigerated and used within 48 h.
• For IV push: Dilute 2 mL of 10 mg/mL solution with compatible IV solution to total volume of 5 mL or 10 mL. Inject over a period of not less than 2 min.
• For IV infusion: Add 2 mL of 10 mg/mL solution to 100 mL of compatible IV solution. Infuse over 15 to 30 min.

Storage/Stability

Store tablets and suspension at controlled room temperature (59° to 86°F). Protect suspension from freezing. Discard any unused suspension after 30 days. Store premixed injection containers at controlled room temperature (77°F). Store injection vials in refrigerator (36° to 46°F). If solution freezes, bring to room temperature; allow sufficient time to solubilize all components.

Drug Interactions

Effects of ketoconazole may be decreased.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Arrhythmia; AV block; palpitation.

CNS

Headache (5%); dizziness (1%); generalized tonic-clonic seizures, psychic disturbances, asthenia, fatigue.

Dermatologic

Toxic epidermal necrolysis (very rare); acne, alopecia, dry skin, flushing, pruritus, rash, urticaria.

EENT

Conjunctival injection, taste disorder, tinnitus.

GI

Diarrhea (2%); constipation (1%); abdominal discomfort, anorexia, dry mouth, nausea, vomiting.

Genitourinary

Gynecomastia (rare).

Hematologic-Lymphatic

Agranulocytosis; leukopenia; pancytopenia; thrombocytopenia (rare).

Hepatic

Abnormal liver enzymes; cholestatic jaundice.

Hypersensitivity

Anaphylaxis, angioedema, fever, orbital or face edema.

Musculoskeletal

Arthralgia; musculoskeletal pain, including cramps.

Respiratory

Bronchospasm.

Precautions

Pregnancy

Category B .

Lactation

Excreted in breast milk.

Children

IV use in children younger than 1 yr of age not adequately studied.

Consult health care provider for children younger than 12 years of age.

Hypersensitivity

Rare cases of anaphylaxis have occurred.

Renal Function

Longer intervals between doses or lower doses may be needed.

Benzyl alcohol

Multidose injection contains benzyl alcohol.

Gastric malignancy

Symptomatic response to famotidine does not preclude gastric malignancy.

Phenylketonurics

OTC chewable Pepcid AC contains phenylalanine 1.4 mg per tablet.

Patient Information

• Injection
• Advise patient or caregiver that medication will be prepared and administered by a health care professional in a health care setting when oral therapy is not feasible. Therapy will be switched to oral therapy when the health care provider believes it is appropriate.

• OTC
• Instruct patient using OTC famotidine tablets, chewable tablets, or gelcaps to carefully read package instructions regarding warnings and dosing instructions.

• Tablets and Oral Suspension
• Advise patient using tablets or suspension to take prescribed dose without regard to meals, but to take with food if stomach upset occurs.
• Advise patient or caregiver using oral suspension to shake suspension vigorously for 5 to 10 sec before measuring dose and to measure and administer prescribed dose using dosing syringe, dosing spoon, or dosing cup.
• Inform patient that antacids may be taken concurrently with famotidine.
• Instruct patient to report any of the following to health care provider: bloody or coffee ground vomit; black tarry stools; recurrent heart burn; recurrent indigestion or abdominal pain; increasing need for antacid use; bothersome side effects (eg, constipation, gas, headache).

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