Famotidine, sold under the brand name Pepcid among others, is a histamine H₂ receptor antagonist medication that decreases

stomach acid Gastric acid or stomach acid is the acidic component – hydrochloric acid – of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other an ...

production. It is used to treat peptic ulcer disease,

gastroesophageal reflux disease Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is a chronic upper gastrointestinal disease in which stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/or ...

, and Zollinger–Ellison syndrome. It is taken

by mouth Oral administration is a route of administration whereby a substance is taken through the Human mouth, mouth, swallowed, and then processed via the digestive system. This is a common route of administration for many medications. Oral administ ...

or by injection into a vein. It begins working within an hour. Common side effects include

headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

abdominal pain Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues. Since the abdomen contains most of the body's vital organs, it can be an indicator of a wide variety of diseases. Given th ...

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

constipation Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The Human feces, stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the ...

, and

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to Balance disorder, disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a ...

. Serious side effects may include

pneumonia Pneumonia is an Inflammation, inflammatory condition of the lung primarily affecting the small air sacs known as Pulmonary alveolus, alveoli. Symptoms typically include some combination of Cough#Classification, productive or dry cough, ches ...

and

seizures A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

. Use in

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

appears safe but has not been well studied, while use during

breastfeeding Breastfeeding, also known as nursing, is the process where breast milk is fed to a child. Infants may suck the milk directly from the breast, or milk may be extracted with a Breast pump, pump and then fed to the infant. The World Health Orga ...

is not recommended. Famotidine was patented in 1979 and came into medical use in 1985. It is available as a

generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ch ...

. In 2022, it was the 49th most commonly prescribed medication in the United States, with more than 13million prescriptions.

Medical uses

Heartburn Heartburn is a burning sensation felt behind the breastbone. It is a symptom that is commonly linked to acid reflux and is often triggered by food, particularly fatty, sugary, spicy, chocolate, citrus, onion-based and tomato-based products. Ly ...

, acid indigestion, and sour stomach * Treatment for gastric and duodenal ulcers * Treatment for pathologic gastrointestinal hypersecretory conditions such as Zollinger–Ellison syndrome and multiple endocrine adenomas * Treatment for

(GERD) * Treatment for

esophagitis Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stoma ...

* Part of a multidrug regimen for ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, Flagellum#bacterial, flagellated, Bacterial cellular morphologies#Helical, helical bacterium. Mutants can have a rod or curved rod shape that exhibits l ...

'' eradication, although omeprazole may be somewhat more effective. * Prevention of NSAID-induced peptic ulcers. * Given to surgery patients before operations to reduce the risk of

aspiration pneumonia Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may incl ...

Pharmacokinetics

Famotidine has a delayed onset of action, beginning after 90 minutes. However, famotidine has a duration of effect of at least . At its peak effect, after administration, famotidine reduces acid secretion by 7.3 mmol per 30 minutes.

Side effects

The most common side effects associated with famotidine use include

, and

. Famotidine may contribute to QT prolongation, particularly when used with other QT-elongating drugs, or in people with poor

kidney function Assessment of kidney function occurs in different ways, using the presence of symptoms and medical sign, signs, as well as measurements using urine tests, blood tests, and medical imaging. Renal physiology, Functions of a healthy kidney include ...

Mechanism of action

Activation of H₂ receptors located on parietal cells stimulates proton pumps to secrete acid into the stomach lumen. Famotidine, an H₂ antagonist, blocks the action of

histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...

on the parietal cells, ultimately reducing acid secretion into the stomach.

Interactions

Unlike

cimetidine Cimetidine, sold under the brand name Tagamet among others, is a histamine H2 receptor antagonist that inhibits stomach acid production. It is mainly used in the treatment of heartburn and peptic ulcers. With the development of proton pump ...

, the first H₂ antagonist, famotidine has a minimal effect on the

cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...

enzyme system and does not appear to interact with as many drugs as other medications in its class. Some exceptions include

antiretroviral The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs as a strategy to control HIV infection. There are several classes of antiretroviral agents that act on different stages of the HIV life-cycle. The use of mu ...

s such as atazanavir, chemotherapeutics such as doxorubicin, and

antifungal An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as ...

medications such as

itraconazole Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given ...

History

Famotidine was developed by Yamanouchi Pharmaceutical Co. It was licensed in the mid-1980s by Merck & Co. and is marketed by a joint venture between Merck and Johnson & Johnson. The imidazole ring of cimetidine was replaced with a 2-guanidinothiazole ring. Famotidine proved to be nine times more potent than

ranitidine Ranitidine, previously sold under the brand name Zantac among others, is a medication used to decrease stomach acid production. It was commonly used in treatment of peptic ulcer disease, gastroesophageal reflux disease, and Zollinger–Ellis ...

, and thirty-two times more potent than

. It was first marketed in 1981. Pepcid RPD orally disintegrating tablets were released in 1999. Generic preparations became available in 2001, e.g. Fluxid ( Schwarz) or Quamatel ( Gedeon Richter Ltd.). In the United States and Canada, a product called Pepcid Complete, which combines famotidine with an

antacid An antacid is a substance which neutralization (chemistry), neutralizes gastric acid, stomach acidity and is used to relieve heartburn, indigestion, or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhe ...

in a chewable tablet to relieve the symptoms of excess stomach acid quickly, is available. In the UK, this product was known as PepcidTwo until its discontinuation in April 2015. Famotidine has poor bioavailibility (50%) due to its low solubility in the high pH of the intestines. Researchers are developing formulations that use gastroretentive drug delivery systems such as floating tablets to increase bioavailability by promoting local delivery (directly into the stomach wall) of these drugs to receptors in the parietal cell membrane.

Society and culture

Certain preparations of famotidine are available over-the-counter (OTC) in various countries. In the United States and Canada, 10 mg and 20 mg tablets, sometimes in combination with an

, Pepcid Complete are available OTC. Larger doses still require a prescription. Famotidine is generally restricted to prescription only in the United Kingdom, although the medication is legally allowed to be sold OTC to persons aged over 16 in supples lasting no more than a fortnight. Formulations of famotidine in combination with

ibuprofen Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used to relieve pain, fever, and inflammation. This includes dysmenorrhea, painful menstrual periods, migraines, and rheumatoid arthritis. It can be taken oral administration, ...

were marketed by Horizon Pharma under the trade name Duexis.

Research

COVID-19

At the start of the

COVID-19 pandemic The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), began with an disease outbreak, outbreak of COVID-19 in Wuhan, China, in December ...

, some doctors observed that anecdotally some hospitalized patients in China may have had better outcomes on famotidine than other patients who were not taking famotidine. This led to hypotheses about use of famotidine in treatment of

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 can vary but often include fever ...

. Famotidine was considered a possible treatment for COVID-19 due to its potential

anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation, fever or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs reduce pain by inhibiting mechan ...

effects. It was thought that famotidine could modify lung inflammation caused by coronaviruses. However, studies have shown that famotidine is not effective in reducing mortality or improving recovery in COVID-19 patients. Famotidine primarily works by blocking the effects of

and has some potential mechanisms of action that may contribute to its anti-inflammatory properties, including the inhibition of the production of certain pro-inflammatory

cytokines Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

such as TNF-alpha and IL-6. Another hypothesis was that famotidine might activate the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

inflammatory reflex to attenuate cytokine storm. Yet another hypothesis was that famotidine can reduce the activation of

mast cell A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a p ...

s and the subsequent release of inflammatory mediators, therefore acting as a mast cell stabilizer. However, while famotidine may have some anti-inflammatory effects, there is currently insufficient evidence to support its use for treating inflammation associated with COVID-19. Therefore, it is not recommended for this purpose.

Other

Small-scale studies have shown inconsistent and inconclusive evidence of efficacy in treatment-resistant

schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...

Veterinary uses

Famotidine is given to dogs and cats with acid reflux.

References

External links

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