H2-histamine receptor antagonist
Brand names: Pepcid AC, Pepcid, Famox, Tamin
Updated · Methodology
Second line
Alternative to proton pump inhibitors in mild-to-moderate GERD when PPIs are intolerable, or for nocturnal acid breakthrough as PPI add-on. Dose 20–40 mg twice daily. Less effective than PPIs – omeprazole and esomeprazole suppress acid 80–95% over 24 hours versus 70% with famotidine. Used for episodic symptoms or nocturnal acidity.
Sources
ICD-10: K21 · ICD-11: DA22
Second line
Used in gastric and duodenal ulcer when PPIs are intolerable, or as maintenance after ulcer healing. Dose 40 mg once daily at bedtime for 4–8 weeks. 2017 sets PPIs plus H. pylori eradication as first-line; H2-blockers remain an alternative.
Sources
ICD-10: K27 · ICD-11: DA61
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Famotidine is an H2-receptor antagonist. It is prescribed for gastric and duodenal peptic ulcer, GERD, and stress ulcer prophylaxis (AEMPS Ficha Técnica). In alt detox circles, famotidine is occasionally promoted for stomach protection in healthy people without a confirmed diagnosis. In people without peptic ulcer disease or GERD, no clinical studies of prophylactic use exist. The drug is relatively safe but on long-term use can cause vitamin B12 deficiency (via reduced gastric acidity), decreased calcium and iron absorption, and confusion in older adults. If famotidine is being taken for detox or stomach protection without confirmed diagnosis, consider seeking a second opinion.
A competitive reversible antagonist of H2 histamine receptors on gastric parietal cells. Reduces basal and food-stimulated hydrochloric acid secretion by 70–90% for 10–12 hours. Compared with other H2-blockers (cimetidine, ranitidine), more selective and does not inhibit CYP enzymes – fewer drug interactions. After ranitidine's 2020 worldwide withdrawal due to N-nitrosodimethylamine (NDMA) contamination, it is the only widely available H2-blocker.
AEMPS summary of product characteristics (section 4.6): famotidine is not recommended in pregnancy and is prescribed only if clearly necessary. Before it is used in a pregnant woman, the potential benefits are weighed against the possible risks.
Compatible with breastfeeding. Milk concentrations are low.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Verbatim lines from the interaction sections, in the language of the label
«Si es posible, debe evitarse la administración conjunta de posaconazol en suspensión oral y famotidina, ya que la famotidina puede reducir la absorción de la suspensión oral de posaconazol durante el…»AEMPS, section 4.5 · Open on CIMA
«Drugs Dependent on Gastric pH for Absorption: See the prescribing information for other drugs dependent on gastric pH for absorption for administration instructions, including atazanavir, erlotinib…»FDA, section 7 · Open on DailyMed
«Drugs Dependent on Gastric pH for Absorption: See the prescribing information for other drugs dependent on gastric pH for absorption for administration instructions, including atazanavir, erlotinib…»FDA, section 7 · Open on DailyMed
«Drugs Dependent on Gastric pH for Absorption: See the prescribing information for other drugs dependent on gastric pH for absorption for administration instructions, including atazanavir, erlotinib…»FDA, section 7 · Open on DailyMed
«Famotidina no interacciona con el sistema enzimático ligado al citocromo P450 que interviene en el metabolismo de algunos fármacos.. En el hombre es improbable que se produzcan interacciones con…»AEMPS, section 4.5 · Open on CIMA
«Famotidina no interacciona con el sistema enzimático ligado al citocromo P450 que interviene en el metabolismo de algunos fármacos.. En el hombre es improbable que se produzcan interacciones con…»AEMPS, section 4.5 · Open on CIMA
«Famotidina no interacciona con el sistema enzimático ligado al citocromo P450 que interviene en el metabolismo de algunos fármacos.. En el hombre es improbable que se produzcan interacciones con…»AEMPS, section 4.5 · Open on CIMA
«Established and Other Potentially Significant Drug Interactions: H 2 -Receptor antagonists ↓ atazanavir Coadministration may result in loss of virologic response and development of resistance. In…»FDA, section 7 · Open on DailyMed
«Otros tratamientos concomitantes: No se observó ninguna interacción farmacocinética o farmacodinámica clínicamente significativa cuando se administró apixabán con atenolol o f amotidina. La…»AEMPS, section 4.5 · Open on CIMA
«Interacción de otros medicamentos con aripiprazol: Famotidina, antagonista H2, bloqueante de los ácidos gástricos, reduce la tasa de absorción de aripiprazol, pero se considera que este efecto no es…»AEMPS, section 4.5 · Open on CIMA
«Drugs Having No Clinically Important Interactions with Aripiprazole: Based on pharmacokinetic studies, no dosage adjustment of aripiprazole is required when administered concomitantly with…»FDA, section 7 · Open on DailyMed
«Antagonistas de los receptores H 2: La administración simultánea de famotidina por vía intravenosa y cefditoreno pivoxilo oral produjo una»AEMPS, section 4.5 · Open on CIMA
«Inhibidores enzimáticos: El antagonista del receptor H 2 de la histamina, cimetidina, que es un inhibidor de múltiples isoenzimas CYP, incluyendo CYP3A4 y CYP2C19, reduce el aclaramiento del diazepam…»AEMPS, section 4.5 · Open on CIMA
«Antiácidos y antagonistas H 2 : La administración conjunta de duloxetina con antiácidos que contengan aluminio y magnesio, o con famotidina no tuvo efecto significativo sobre la velocidad y magnitud…»AEMPS, section 4.5 · Open on CIMA
«Drugs that Affect Gastric Acidity: Duloxetine delayed-release capsules have an enteric coating that resists dissolution until reaching a segment of the gastrointestinal tract where the pH exceeds…»FDA, section 7 · Open on DailyMed
«Drugs Without Clinically Significant Interactions with Efavirenz: No dosage adjustment is recommended when efavirenz is given with the following: aluminum/FDA, section 7 · Open on DailyMed
«Drug Interactions:: famotidine rifabutin»FDA, section 7 · Open on DailyMed
«CYP450 Interactions: CYP1A2 acyclovir, allopurinol, caffeine, cimetidine, ciprofloxacin, disulfiram, enoxacin, famotidine, fluvoxamine, methoxsalen, mexiletine, norfloxacin, oral contraceptives…»FDA, section 7 · Open on DailyMed
Opens the checker prefilled with this drug. Pick the second one from your regimen.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Famotidine is evaluated for the following indications with varying evidence strength: Peptic ulcer disease (evidence tier B), Gastroesophageal reflux disease (evidence tier B), Body detoxification and cleansing (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of Famotidine (≥ 1 in 100): Headache, Dizziness, Constipation or diarrhea, Dry mouth. See the Safety section for uncommon and serious reactions.
AEMPS summary of product characteristics (section 4.6): famotidine is not recommended in pregnancy and is prescribed only if clearly necessary. Before it is used in a pregnant woman, the potential benefits are weighed against the possible risks.
Compatible with breastfeeding. Milk concentrations are low.
Famotidine is contraindicated in: Famotidine or other H2-blocker hypersensitivity; Severe renal impairment without dose adjustment. Full list in the Safety section.
Direct links to regulator labels. Open in a new tab.
Lansoprazole, Magnesium hydroxide, Mastic gum, Omeprazole, Slippery elm (inner bark), Almagate, Pantoprazole, Rabeprazole