Famotidine

 Actions Reversibly and competitively blocks histamine at H2 receptors, particularly those in gastric parietal cells, leading to inhibition of gastric acid secretion.

 Indications Short-term treatment and maintenance therapy for duodenal ulcer, gastroesophageal reflux disease (GERD, including erosive or ulcerative disease), benign gastric ulcer, treatment of pathologic hypersecretory conditions.

Treatment of upper GI bleeding; prevention of stress ulcers; prior to anesthesia for prevention of pulmonary aspiration of gastric acid.

 Contraindications Hypersensitivity to other H2 antagonists.

 Route/Dosage

Duodenal Ulcer (Active)

PO 40 mg at bedtime or 20 mg bid for 6 to 8 wk. Maintenance: 20 mg at bedtime.

Benign Gastric Ulcer (Acute)

40 mg at bedtime.

GERD

ADULTS: 20 mg bid (max 6 wk). For esophagitis and accompanying symptoms caused by GERD, 20 to 40 mg bid (max 12 wk).

Pathologic Hypersecretory Conditions

ADULTS: Start at 20 mg q 6 hr, continued as clinically indicated; doses up to 160 mg q 6 hr have been used.

Moderate or Severely Impaired Renal Function

(Ccr < 10 mL/min) May need to reduce to half the dose or increase dosing interval to 36 to 48 hr.

Parenteral For hospitalized patients with pathologic hypersecretory conditions or intractable ulcers, or patients unable to take orally: 20 mg IV q 12 hr. Parenteral use in GERD not established.

 Interactions

Ketoconazole: Effects of ketoconazole may be decreased.

 Lab Test Interferences None well documented.

 Adverse Reactions

CARDIOVASCULAR: Palpitations. CNS: Headache; somnolence; fatigue; dizziness; confusion; hallucinations; agitation or anxiety; depression; insomnia; paresthesias. DERMATOLOGIC: Alopecia; rash; pruritus; urticaria; acne; dry skin; flushing. EENT: Tinnitus; taste disorder; orbital edema; conjunctival injection. GI: Diarrhea; constipation; nausea; vomiting; abdominal discomfort; anorexia; dry mouth. GU: Impotence; loss of libido. HEMATOLOGIC: Thrombocytopenia. RESPIRATORY: Bronchospasm. OTHER: Arthralgia; transient pain at injection site; fever.

 Precautions

Pregnancy: Category B. Lactation: Undetermined. CHILDREN: Safety and efficacy not established. Elderly: May have reduced renal function; decreased clearance may occur. Gastric Malignancy: Symptomatic response to famotidine does not preclude gastric malignancy. Hepatic Function Impairment: Use caution; decreased clearance may occur. Hypersensitivity: Rare cases of anaphylaxis have occurred. Renal Function Impairment: Decreased clearance may occur; reduced dose may be needed.

 Administration/Storage

• To prepare for IV push, dilute 2 mL famotidine (solution containing 10 mg/mL) with 0.9% Sodium Chloride for Injection in 5 to 10 mL volume. Administer over 2 min.
• To prepare IV infusion, dilute 2 mL famotidine (solution containing 10 mg/mL) with 100 mL 5% Dextrose. Other diluents that may be used include 0.9% Sodium Chloride for Injection, 10% Dextrose, Lactated Ringer’s Injection, or 5% sodium bicarbonate. Infuse over 15 to 30 min.
• Keep powder vials away from heat. After reconstitution, store in the refrigerator, but do not freeze. Discard after 30 days.
• Store parenteral solutions in refrigerator. When mixed in polyvinyl chloride minibags, stability is 14 days in refrigerator; if frozen, solution remains stable for 28 days and for 48 hr at room temperature.
• Administer with antacids if necessary.
• Medication may be mixable with TPN. Stability depends on solution used.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Monitor renal and hepatic function in elderly patients. Notify health care provider of any changes in hepatic or renal function.
• Monitor fluid I&O for possible dosage adjustment.
• Give with antacids if necessary.

 Patient/Family Education

• Instruct patient not to double up on medication if dose is missed, but to wait and take next scheduled dose on time.
• Tell patient to notify health care provider immediately of any black, tarry stool or “coffee-ground” vomit.
• Tell patient to notify health care provider of any shortness of breath, GI disturbances, bleeding, rash, dizziness, or fever.
• Tell patient to shake suspension well before taking.