An antacid is a substance which neutralizes stomach acidity and is used to relieve

heartburn Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the ...

indigestion Indigestion, also known as dyspepsia or upset stomach, is a condition of impaired digestion. Symptoms may include upper abdominal fullness, heartburn, nausea, belching, or upper abdominal pain. People may also experience feeling full earlier t ...

or an upset stomach. Some antacids have been used in the treatment of

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

and

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

. Marketed antacids contain salts of

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

, or

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

. Some preparations contain a combination of two salts, such as

magnesium carbonate Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals. Forms The most common magnesium carbonate forms are ...

and

aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric, i.e., it has both basic ...

(e.g.

hydrotalcite Hydrotalcite or formerly also Völknerite is a layered double hydroxide (LDH) of general formula ·4, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate ions exi ...

Medical uses

Antacids are available over the counter and are taken by mouth to quickly relieve occasional

, the major symptom of

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

and

. Treatment with antacids alone is symptomatic and only justified for minor symptoms.U.S. Department of Health & Human Services. Agency for Healthcare Research and Quality 23 September 201
Consumer Summary – Treatment Options for GERD or Acid Reflux Disease: A Review of the Research for Adults
Alternative uses for antacids include constipation, diarrhea, hyperphosphatemia, and urinary alkalization. Some antacids are also used as an adjunct to pancreatic enzyme replacement therapy in the treatment of pancreatic insufficiency. Non-particulate antacids (

sodium citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...

) increase gastric pH with little or no effect on gastric volume, and therefore may see some limited use in pre-operative procedures. Sodium citrate should be given within 1 hour of surgery to be the most effective.

Side effects

Conventional effervescent tablets contain a significant amount of

and are associated with increased odds of adverse cardiovascular events according to an 2013 study. Alternative sodium-free formulations containing magnesium salts may cause diarrhea, whereas those containing

may cause

. Rarely, long-term use of calcium carbonate may cause

kidney stones Kidney stone disease, also known as nephrolithiasis or urolithiasis, is a crystallopathy where a calculus (medicine), solid piece of material (kidney stone) develops in the urinary tract. Kidney stones typically form in the kidney and leave the ...

. Long-term use of antacids containing

may increase the risk of developing

osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone a ...

.U.S. Department of Health and Human Services, National Institutes of Health, U.S. National Library of Medicine. Page last updated: 7 November 201
Medline Plus: Taking Antacids
/ref>

In vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology a ...

studies have found a potential for acid rebound to occur due to antacid overuse, however the significance of this finding has been called into question.

Properties of antacids

When an excess amount of acid is produced in the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, the natural mucous barrier that protects the lining of the stomach can

degrade Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...

, leading to

pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

and

irritation Irritation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant. Irritants are typically thought of as chemical age ...

. There is also potential for the development of

acid reflux Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...

, which can cause pain and damage to the

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to t ...

. Antacids contain

alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

ions that chemically neutralize stomach

gastric acid Gastric acid, gastric juice, or stomach acid is a digestive fluid formed within the stomach lining. With a pH between 1 and 3, gastric acid plays a key role in digestion of proteins by activating digestive enzymes, which together break down the ...

, reducing damage to the stomach lining and

, and relieving pain. Some antacids also inhibit pepsin, an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

that can damage the

. Antacids do not directly inhibit acid

secretion 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classic ...

, and thus are distinct from acid-reducing drugs like H₂-receptor antagonists or proton pump inhibitors. Antacids do not kill the bacteria '' Helicobacter pylori'', which causes most ulcers.

Interactions

Basic structure of tetracycline chelating a metal

Antacids are known to

interact Advocates for Informed Choice, doing business as, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex trai ...

with several oral medications, including fluoroquinolone and

tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. Common side effects in ...

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

, itraconazole, and

prednisone Prednisone is a glucocorticoid medication mostly used to suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium due to cancer and ad ...

. Metal chelation is responsible for some of these interactions (e.g. fluoroquinolones,

tetracyclines Tetracyclines are a group of broad-spectrum antibiotic compounds that have a common basic structure and are either isolated directly from several species of ''Streptomyces'' bacteria or produced semi-synthetically from those isolated compounds. T ...

), leading to decreased absorption of the chelated drug. Some interactions may be due to the pH increase observed in the

following antacid

ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms in ...

, leading to increased absorption of weak acids, and decreased absorption of weak bases. Antacids also cause an increase in pH of the

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...

(alkalization), which may cause increased

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

concentrations of weak bases, and increased

excretion Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after ...

of weak acids. A proposed method to mitigate the effects of

acidity and chelation on drug absorption is to space out the administration of antacids with interacting

medications A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and re ...

, however this method has not been well studied for drugs affected by urine alkalization. There are concerns regarding interactions between delayed-release tablets and antacids, as antacids may increase the stomach pH to a point at which the coating of the delayed-release tablet will dissolve, leading to degradation of the drug if it is pH sensitive.

Formulations

Antacids may be formulated with other

active ingredients An active ingredient is any ingredient that provides biologically active or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease or to affect the structure or any function of the body of humans or animals. Th ...

such as simethicone to control gas, or alginic acid to act as a physical barrier to acid.

Liquids

Several liquid antacid preparations are

marketed Marketing is the process of exploring, creating, and delivering value to meet the needs of a target market in terms of goods and services; potentially including selection of a target audience; selection of certain attributes or themes to emph ...

. Common liquid preparations include

milk of magnesia Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...

and magnesium/aluminum combinations. A potential advantage of using a liquid preparation over a tablet is that liquids may provide quicker relief, however this may coincide with a shorter duration of action.

Tablets

Chewable tablets

Chewable tablets are one of the most common forms of antacids, and are readily available over-the-counter. Upon reaching the

, the tablet powder will dissolve in the stomach acid, allowing the cations to be released and neutralize excess stomach acid. Common salts available in tablet form include those of calcium, magnesium, aluminum, and sodium. Some common brand are

Tums Tums (stylized as TUMS) is an antacid made of sucrose (sugar) and calcium carbonate (CaCO3) manufactured by Haleon in St. Louis, Missouri, US. They are also available in a sugar-free version. It is an over-the-counter drug, available at many ...

, Gaviscon chewable tablets and Maalox chewable tablets.

Effervescent tablets

Effervescent tablets are tablets which are designed to dissolve in

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

, and then release

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

. Common ingredients include

citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...

and

sodium bicarbonate Sodium bicarbonate ( IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3− ...

, which react when in contact with water to produce

. Effervescent antacids may also contain

aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...

sodium carbonate Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

, or

tartaric acid Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...

. Those containing aspirin may cause further gastric irritation and ulceration due to

's effects on the mucous membrane of the

. Common

brands A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...

include

Alka-Seltzer Alka-Seltzer is an effervescent antacid and pain reliever first marketed by the Dr. Miles Medicine Company of Elkhart, Indiana, United States. Alka-Seltzer contains three active ingredients: aspirin (acetylsalicylic acid) (ASA), sodium bicarbo ...

, Gaviscon, and

Eno Eno may refer to: Music * English National Opera, London * ''Eno'', an album by Japanese band Polysics * "Eno", a song by X-Wife from '' Rockin' Rio EP'' Organisations and businesses * Eno (company), a Chinese clothing and accessories busine ...

References

External links

* {{Portal bar, Medicine