famotidine
Pepcid, Pepcid AC, Pepcid AC Acid Controller, Pepcid RPD

Available forms
Available by prescription only
Injection: 10 mg/ml
Injection, premixed: 20 mg/50 ml normal saline solution
Suspension: 40 mg/5 ml
Tablets: 20 mg, 40 mg
Tablets (orally disintegrating): 20 mg, 40 mg

Available without a prescription (Pepcid AC)
Gelcaps: 10 mg
Tablets: 10 mg
Tablets (chewable): 10 mg

Indications and dosages
 Duodenal and gastric ulcer. Adults: For acute therapy, 40 mg P.O. h.s. for 4 to 8 weeks; for maintenance therapy, 20 mg P.O. h.s.
 Pathologic hypersecretory conditions (such as Zollinger-Ellison syndrome). Adults: 20 mg P.O. q 6 hours. As much as 160 mg q 6 hours may be administered.
 Short-term treatment of gastroesophageal reflux disease. Adults: 20 to 40 mg P.O. b.i.d. for up to 12 weeks.
 Hospitalized patients with intractable ulcers or hypersecretory conditions or patients who can’t take oral drugs; patients with GI bleeding; to control gastric pH in critically ill patients. Adults: 20 mg I.V. q 12 hours.
 Prevention or treatment of heartburn. Adults and children age 12 and older: 1 tablet (Pepcid AC) P.O. when symptoms occur; or 10 mg P.O. 1 hour before meals to prevent symptoms. Drug can be used b.i.d. if needed.
≡ Dosage adjustment. For patients with severe renal insufficiency (creatinine clearance less than 10 ml/minute), dosage may be reduced to 20 mg h.s., or the dosing interval may be prolonged to 36 to 48 hours to avoid excess accumulation of drug.

Pharmacodynamics
Antiulcer action: Famotidine competitively inhibits action of histamine at H₂-receptors in gastric parietal cells. This inhibits basal and nocturnal gastric acid secretion from stimulation by such factors as caffeine, food, and pentagastrin.

Pharmacokinetics
Absorption: When administered orally, about 40% to 45% of dose is absorbed.
Distribution: Distributed widely to many body tissues.
Metabolism: About 30% to 35% of an administered dose is metabolized by the liver.
Excretion: Most is excreted unchanged in urine. Famotidine has a longer duration of effect than its 2 1/2- to 4-hour half-life suggests.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug.

Interactions
Drug-drug. Enteric-coated drugs: Enteric coatings may dissolve too rapidly because of increased gastric pH. Use together cautiously.
Ketoconazole: Decreases ketoconazole absorption. Increase ketoconazole dosage if needed.

Adverse reactions
CNS: headache, dizziness, vertigo, malaise, paresthesia, fever.
CV: palpitations, flushing.
EENT: tinnitus, orbital edema.
GI: taste disorder, diarrhea, constipation, anorexia, dry mouth.
Musculoskeletal: musculoskeletal pain.
Skin: acne, dry skin.
Other: transient irritation at I.V. site.

Effects on lab test results
• May increase BUN, creatinine, and liver enzyme levels.

Overdose and treatment
Overdose hasn’t been reported. Treatment should include gastric lavage or induced emesis, followed by activated charcoal to prevent further absorption and supportive and symptomatic therapy. Hemodialysis doesn’t remove famotidine.

Special considerations
• Drug isn’t recommended for use longer than 8 weeks in patients with uncomplicated duodenal ulcer.
• After administration via nasogastric tube, flush tube to clear it and ensure passage of drug to stomach.
• Antacids may be administered concurrently.
• Drug appears to cause fewer adverse reactions and drug interactions than cimetidine.
• Drug may antagonize pentagastrin during gastric acid secretion tests. In skin tests using allergen extracts, drug may cause false-negative results.
 ALERT Don’t confuse famotidine with felodipine.
• Monitor patient as needed for all H₂-receptor antagonists.
Pregnant patients
• Use drug during pregnancy only when clearly indicated.
Breast-feeding patients
• Drug may appear in breast milk. Use cautiously in breast-feeding women.
Geriatric patients
• Use drug cautiously in elderly patients because of increased risk of adverse reactions, particularly those affecting the CNS.

Patient education
• Caution patient to take drug only as directed and to continue taking doses, even after pain subsides, to ensure adequate healing.
• Instruct patient to take dose at bedtime.
• Tell patient to open RPD tablet blisters with dry hands; place tablet on tongue and let melt. Swallow with saliva.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use