Famotidine Drug Profile

What is Famotidine?

Famotidine is an oral medication that belongs to a class of drugs called histamine-2 (H2) receptor antagonists, also known as H2 blockers. It is primarily used to reduce stomach acid production and treat conditions related to excess gastric acid, including heartburn, acid reflux, and peptic ulcers. Famotidine is available both over-the-counter and by prescription in higher strengths.

Uses

Famotidine has several approved medical uses:

• Gastroesophageal reflux disease (GERD): Reduces stomach acid that backs up into the esophagus, relieving heartburn and preventing esophageal damage
• Peptic ulcer treatment: Helps heal stomach and duodenal ulcers by decreasing acid production that can irritate ulcerated tissue
• Ulcer prevention: Used in patients taking nonsteroidal anti-inflammatory drugs (NSAIDs) who are at risk for developing stomach ulcers
• Zollinger-Ellison syndrome: Manages this rare condition characterized by excessive stomach acid production due to gastrin-secreting tumors
• Heartburn relief: Provides symptomatic relief from occasional heartburn and acid indigestion

How it works

Famotidine works by blocking histamine-2 receptors located on acid-producing cells in the stomach lining. When histamine binds to these receptors, it normally stimulates the production of stomach acid. By blocking this interaction, famotidine significantly reduces the amount of acid the stomach produces, typically decreasing acid secretion by 60-70% for up to 12 hours after a single dose.

Side effects

Common side effects include:

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• Headache
• Dizziness
• Constipation
• Diarrhea
• Fatigue or drowsiness
• Nausea
• Abdominal discomfort
• Dry mouth

Serious side effects requiring immediate medical attention:

• Irregular heartbeat or palpitations
• Severe muscle pain or weakness
• Mental confusion or hallucinations
• Severe allergic reactions (difficulty breathing, swelling of face or throat)
• Signs of liver problems (yellowing of skin or eyes, dark urine)

Warnings and precautions

• Kidney disease: Patients with reduced kidney function may need dosage adjustments, as famotidine is primarily eliminated through the kidneys
• Pregnancy and breastfeeding: Classified as FDA pregnancy category B, generally considered safe during pregnancy, but should be used only when clearly needed and under medical supervision
• Elderly patients: May be more susceptible to confusion and other central nervous system side effects, particularly those with kidney impairment
• Masking symptoms: May mask symptoms of serious gastric conditions, including gastric cancer; persistent symptoms should be properly evaluated before treatment
• Long-term use: Prolonged acid suppression may increase risk of certain infections and nutrient deficiencies, particularly vitamin B12 and magnesium

Interactions

• Ketoconazole and itraconazole: Famotidine reduces stomach acid needed for proper absorption of these antifungal medications
• Atazanavir and other HIV protease inhibitors: Decreased absorption due to reduced stomach acidity may lead to treatment failure
• Iron supplements: Reduced gastric acid may impair iron absorption, potentially leading to iron deficiency
• Digoxin: May slightly increase digoxin blood levels, requiring monitoring in patients on narrow therapeutic ranges
• Warfarin: Potential for altered anticoagulant effects, though interactions are generally mild
• Calcium carbonate supplements: Reduced acid may decrease calcium absorption from carbonate forms
• Dasatinib: This cancer medication requires acidic environment for absorption; concurrent use should be avoided
• Sucralfate: Should be taken at least 2 hours apart from famotidine to avoid absorption interference

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Dosage

Typical adult dosages vary depending on the condition being treated:

• Heartburn/GERD: 20 mg twice daily or 40 mg once daily at bedtime
• Peptic ulcer treatment: 40 mg once daily at bedtime or 20 mg twice daily for 4-8 weeks
• Ulcer prevention: 20 mg twice daily
• Over-the-counter use: 10-20 mg up to twice daily for symptom relief

Dosages should be reduced in patients with significant kidney impairment. Always follow your healthcare provider’s specific dosing instructions, as individual needs may vary based on medical condition, response to treatment, and other factors.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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