famotidine

Action

Blocks action of histamine at histamine₂-receptor sites in gastric parietal cells, inhibiting gastric acid secretion and stabilizing pepsin

Availability

Gelcaps: 10 mg

Oral suspension: 40 mg/5 ml

Solution for injection: 10 mg/ml, 20 mg/50 ml of normal saline solution

Tablets: 10 mg, 20 mg, 40 mg

Tablets (chewable): 10 mg

Tablets (orally disintegrating): 20 mg, 40 mg

Indications and dosages

➣ Active duodenal ulcers and benign gastric ulcers

Adults: 40 mg P.O. once daily at bedtime or 20 mg P.O. b.i.d. for up to 8 weeks

➣ Prophylaxis of duodenal ulcers

Adults: 20 mg P.O. once daily at bedtime

➣ Gastroesophageal reflux disease

Adults: 20 mg P.O. b.i.d. for up to 6 weeks. Maximum dosage is 40 mg b.i.d. for up to 12 weeks.

Children ages 1 to 16: 1 mg/kg P.O. daily in two divided doses, to a maximum of 40 mg b.i.d.

Infants ages 3 months to 1 year: 0.5 mg/kg P.O. b.i.d. for up to 8 weeks

Infants younger than age 3 months: 0.5 mg/kg P.O. once daily for up to 8 weeks

➣ Gastric hypersecretory conditions (such as Zollinger-Ellison syndrome)

Adults: Initially, 20 mg P.O. q 6 hours, increased as needed to 160 mg q 6 hours

➣ Hospitalized patients with pathologic hypersecretory conditions or ulcers; patients who can't take oral drugs

Adults: 20 mg I.V. q 12 hours

➣ Prevention or treatment of heartburn, acid indigestion, and sour stomach (Pepcid AC only)

Adults: For prevention, 10 mg P.O. 1 hour before eating, or 10-mg chewable tablet 15 minutes before eating, to a maximum of 20 mg/24 hours for up to 2 weeks. For symptomatic treatment, 10 mg P.O. once or twice daily.

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug or other histamine₂-receptor antagonists

Precautions

Use cautiously in:

• renal impairment with prolonged QT interval and seizures (very rare)

• elderly patients

• pregnant or breastfeeding patients.

Administration

• Be aware that drug usually is given in one daily dose to patients with renal insufficiency.

• Give P.O. form with foods or liquids.

• Dilute I.V. form with 10 ml dextrose 5% in water or normal saline solution (100 ml) for I.V. piggyback administration.

• Deliver by I.V. push over 2 minutes or intermittent infusion over 30 minutes.

• Know that drug may cause transient irritation at I.V. site.

Adverse reactions

CNS: dizziness, headache, paresthesia, asthenia, fatigue, insomnia, somnolence, psychic disturbances

CV: palpitations, arrhythmias, AV block

GI: nausea, vomiting, diarrhea, constipation, dry mouth, anorexia, cholestatic jaundice, abdominal pain

GU: decreased libido

Hematologic: agranulocytosis, pancytopenia, leukopenia, thrombocytopenia (rare)

Hepatic: liver enzyme abnormalities, hepatitis

EENT: orbital edema, conjunctival redness, tinnitus

Musculoskeletal: musculoskeletal pain, muscle cramps, arthralgia

Respiratory: bronchospasm, interstitial pneumonia

Skin: flushing, acne, dry skin, rash, urticaria, alopecia, pruritus; epidermal necrolysis and Stevens-Johnson syndrome (very rare)

Other: altered taste, fever, pain at injection site, hypersensitivity reactions including anaphylaxis and angioedema

Interactions

Drug-diagnostic tests. Liver enzymes: altered levels

Patient monitoring

• Assess patient for GI signs and symptoms.

• Monitor blood urea nitrogen and creatinine levels in patients with renal impairment.

☞ Monitor patient for prolonged QT interval and seizures, which have been reported very rarely in patients with impaired renal function whose famotidine dosage or dosing interval may not have been adjusted appropriately. Also monitor patient for arrhythmia and AV block.

☞ Monitor patient for signs and symptoms of epidermal necrolysis, Stevens-Johnson syndrome, and hematologic or respiratory changes.

Patient teaching

• Tell patient that drug is most effective when taken at bedtime.

• Inform patient that pain relief may not begin until several days after therapy starts.

☞ Instruct patient to take drug exactly as prescribed and to immediately report cardiovascular signs and symptoms, seizures, and hematologic or respiratory changes.

• Tell female patient to inform prescriber if she is pregnant or breastfeeding.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the tests mentioned above.