From the Guidelines
Famotidine is an H2 blocker used to treat and prevent heartburn, acid indigestion, and other symptoms caused by excess stomach acid. The typical adult dose is 10-20 mg taken orally once or twice daily as needed, or as directed by a healthcare provider, with a maximum dose of 40 mg twice daily 1. Famotidine works by reducing the amount of acid produced in the stomach by blocking histamine receptors in the stomach lining, which normally stimulate acid production when activated 1.
Key Points
- Famotidine is often used as an alternative to proton pump inhibitors (PPIs) in patients taking dual-antiplatelet therapy, as PPIs may interfere with the metabolism of clopidogrel 1.
- The FAMOUS trial found that famotidine 20 mg twice daily was beneficial in reducing the incidence of peptic ulcer or esophagitis in patients taking low-dose aspirin 1.
- While generally safe for most people, those with kidney problems may need dose adjustments, and common side effects can include headache, dizziness, and constipation 1.
Important Considerations
- The use of H2 blockers like famotidine may be preferred over PPIs in certain situations, such as in patients taking clopidogrel, due to the potential for drug interactions 1.
- The dosage of famotidine should be limited to 40 mg twice daily, as defined by the Society of Critical Care Medicine and American Society of Health-System Pharmacists guideline for the prevention of stress-related gastrointestinal bleeding in critically ill adults 1.
From the FDA Drug Label
The active ingredient in Famotidine tablets is a histamine-2 (H2) receptor antagonist. Famotidine is N’-(aminosulfonyl)-3-[[[2-[(diaminomethylene)amino]-4-thiazolyl]methyl]thio]propanimidamide. Famotidine is a histamine-2 (H2) receptor antagonist. It is a competitive inhibitor of histamine-2 (H2) receptors, which primarily functions to inhibit gastric secretion.
- Key characteristics:
From the Research
Definition and Mechanism of Action
- Famotidine is a highly selective histamine H2-receptor antagonist 3
- It is a competitive histamine H2-receptor antagonist, with its main pharmacodynamic effect in humans being the inhibition of gastric acid secretion 4
- Famotidine is approximately 20 to 50 times more potent at inhibiting gastric acid secretion than cimetidine and 8 times more potent than ranitidine on a weight basis 3
Pharmacokinetic Properties
- After oral administration, antisecretory activity begins within 1 h, reaches a maximum in 1-3 h, and lasts 10-12 h 4
- Oral famotidine is incompletely absorbed, reaching peak plasma concentrations in 1-3 h 4
- It is eliminated primarily through the kidneys (about 70%), mostly as the parent compound, with an average elimination half-life in healthy subjects of 2.8 h 4
Therapeutic Use
- Famotidine is effective in healing both duodenal and gastric ulcers, with healing rates and symptom relief similar or superior to those achieved by cimetidine or ranitidine 3
- It is also effective in preventing recurrence of duodenal ulcer and in the treatment of gastritis and reflux gastro-oesophagitis 3, 5
- Famotidine has been shown to be effective in the treatment of Zollinger-Ellison syndrome, with a longer duration of action than ranitidine or cimetidine 6, 7
Safety and Tolerability
- Famotidine is very well tolerated and is free of the antiandrogenic effects infrequently reported with cimetidine 3
- It does not alter hepatic metabolism of drugs and has not been shown to have clinically important interactions with other drugs 3, 4
- Famotidine appears to be a suitable and well-tolerated alternative to cimetidine and ranitidine for healing peptic ulcers 5