Antacid
Overview
 
An antacid is a substance which neutralizes stomach acidity
Gastric acid
Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...

.
Antacids perform a neutralization reaction, increasing the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 to reduce acidity in the stomach. When gastric hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 reaches the nerves in the gastrointestinal mucosa, they signal pain
Nociception
Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...

 to the central nervous system. This happens when these nerves are exposed.
Antacids are taken by mouth to relieve heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...

, the major symptom of gastroesophageal reflux disease
Gastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...

, or acid indigestion.
Encyclopedia
An antacid is a substance which neutralizes stomach acidity
Gastric acid
Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...

.

Mechanism of action

Antacids perform a neutralization reaction, increasing the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 to reduce acidity in the stomach. When gastric hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 reaches the nerves in the gastrointestinal mucosa, they signal pain
Nociception
Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue...

 to the central nervous system. This happens when these nerves are exposed.

Indications

Antacids are taken by mouth to relieve heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...

, the major symptom of gastroesophageal reflux disease
Gastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...

, or acid indigestion. Treatment with antacids alone is symptomatic and only justified for minor symptoms. The treatment of ulcers may require H2-receptor antagonist
H2-receptor antagonist
The H2 receptor antagonists are a class of drugs used to block the action of histamine on parietal cells in the stomach, decreasing the production of acid by these cells. H2 antagonists are used in the treatment of dyspepsia, although they have been surpassed in popularity by the more effective ...

s, proton pump inhibitor
Proton pump inhibitor
Proton-pump inhibitors are a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production. They are the most potent inhibitors of acid secretion available today. The group followed and has largely superseded another group of pharmaceuticals with similar...

s and eradication of H. pylori.

Side effects

Excess calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 from supplements, fortified food and high-calcium diets, can cause milk-alkali syndrome
Milk-alkali syndrome
In medicine, milk-alkali syndrome, also called Burnett's syndrome in honour of Charles Hoyt Burnett, the American physician who first described it, is characterized by hypercalcemia caused by repeated ingestion of calcium and absorbable alkali...

, which has serious toxicity and can be fatal. In 1915, Bertram Sippy introduced the "Sippy regimen" of hourly ingestion of milk and cream, the gradual addition of eggs and cooked cereal, for 10 days, combined with alkaline powders, which provided symptomatic relief for peptic ulcer disease. Over the next several decades, the Sippy regimen resulted in renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...

, alkalosis
Alkalosis
Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma . Generally, alkalosis is said to occur when pH of the blood exceeds 7.45. The opposite condition is acidosis .-Causes:...

, and hypercalcaemia
Hypercalcaemia
Hypercalcaemia is an elevated calcium level in the blood. . It can be an asymptomatic laboratory finding, but because an elevated calcium level is often indicative of other diseases, a workup should be undertaken if it persists...

, mostly in men with peptic ulcer disease. These adverse effects were reversed when the regimen stopped, but it was fatal in some patients with protracted vomiting. Milk alkali syndrome declined in men after effective treatments were developed for peptic ulcer disease. But during the past 15 years, it has been reported in women taking calcium supplements above the recommended range of 1200 to 1500 mg daily, for prevention and treatment of osteoporosis
Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...

, and is exacerbated by dehydration. Calcium has been added to over-the-counter products, which contributes to inadvertent excessive intake.
The New England Journal of Medicine
New England Journal of Medicine
The New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It describes itself as the oldest continuously published medical journal in the world.-History:...

 reported a typical case of a woman who arrived in the emergency department vomiting and in altered mental status, writhing in pain. She had consumed large quantities of chewable antacid tablets containing calcium carbonate. She gradually recovered.

Compounds containing calcium may also increase calcium output in the urine, which might be associated with kidney stones. Calcium salts may cause constipation
Constipation
Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...

.

Other adverse effects from antacids include:
  • Carbonate
    Carbonate
    In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

    : regular high doses may cause alkalosis
    Alkalosis
    Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma . Generally, alkalosis is said to occur when pH of the blood exceeds 7.45. The opposite condition is acidosis .-Causes:...

    , which in turn may result in altered excretion of other drugs, and kidney stones. A chemical reaction between the carbonate and hydrochloric acid may produce carbon dioxide gas. This causes gastric distension which may not be well tolerated. Carbon dioxide formation can also lead to headaches and decreased muscle flexibility.
  • Aluminum hydroxide: may lead to the formation of insoluble aluminium-phosphate-complexes, with a risk for hypophosphatemia
    Hypophosphatemia
    Hypophosphatemia is an electrolyte disturbance in which there is an abnormally low level of phosphate in the blood. The condition has many causes, but is most commonly seen when malnourished patients are given large amounts of carbohydrates, which creates a high phosphorus demand by cells,...

     and osteomalacia
    Osteomalacia
    Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism...

    . Although aluminium
    Aluminium
    Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

     has a low gastrointestinal absorption, accumulation may occur mainly in the presence of renal insufficiency. Aluminium-containing drugs often cause constipation
    Constipation
    Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...

     and are neurotoxic. Aluminium-containing drugs are contraindicated in pregnancy.
  • Magnesium hydroxide
    Magnesium hydroxide
    Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite....

    : has laxative
    Laxative
    Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...

     properties. Magnesium may accumulate in patients with renal failure
    Renal failure
    Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...

     leading to hypermagnesemia
    Hypermagnesemia
    Hypermagnesemia is an electrolyte disturbance in which there is an abnormally elevated level of magnesium in the blood. Usually this results in excess of magnesium in the body....

    , with cardiovascular and neurological complications. See Milk of magnesia.
  • Sodium: increased intake of sodium may be deleterious for arterial hypertension, heart failure and many renal diseases.


Side effects from antacids vary depending on individual and other medications they may be taking at the time. Those who experience side effects most commonly suffer from changes in bowel functions, such as diarrhea, constipation, or flatulence.

Although reactions to any drug may vary from person to person, generally those medications that contain aluminum or calcium are the likeliest to cause constipation, those that contain magnesium are the likeliest to cause diarrhea. Some products combine these ingredients, which essentially cancels them out, to forestall unpleasant side effects.

Some well-known antacid brands

  • Alka-Seltzer
    Alka-Seltzer
    Alka-Seltzer is an effervescent antacid and pain reliever first marketed by the Dr. Miles Medicine Company. It was developed by Treneer in Elkhart Indiana. Alka-Seltzer is marketed for relief of minor aches, pains, inflammation, fever, headache, heartburn, sour stomach, indigestion, and hangovers,...

     – NaHCO3 and/or KHCO3
  • Andrews Antacid – CaCO3 MgCO3
  • Brioschi
    Brioschi
    Brioschi is an Italian company founded in 1907 as Achille Brioschi & C. to "produce and make commerce of chemicals, liquors and similars"; in 1914 the society was quoted on the Milan stock exchange...

     – CHNaO3 (only FDA approved All-Natural)
  • Equate – Al(OH)3 and Mg(OH)2
  • Gaviscon
    Gaviscon
    Gaviscon is a non-prescription medication for the treatment of heartburn and GERD. It is produced and distributed in the UK by Reckitt Benckiser and by GlaxoSmithKline in the US and Canada.Gaviscon is taken to treat heartburn, similarly to other antacids...

     – Al(OH)3
  • Maalox
    Maalox
    Maalox is a brand name antacid containing aluminium hydroxide and magnesium hydroxide to neutralize or reduce stomach acid.Maalox helps relieve symptoms of excessive stomach acidity in patients with indigestion, heartburn, gastroesophageal reflux disease, or stomach or duodenal ulcers. In large...

     (liquid) – Al(OH)3 and Mg(OH)2
  • Maalox (tablet) – CaCO3
  • Milk of Magnesia – Mg(OH)2
  • Pepto-Bismol
    Bismuth subsalicylate
    Bismuth subsalicylate, with a nominal chemical formula of C7H5BiO4, It is a colloidal substance obtained by hydrolysis of bismuth salicylate . The actual structure is unknown and the formulation is only approximate. Recent evidence indicates that it is composed of a bismuth oxide core structure...

     – C7H5BiO4
  • Pepto-Bismol Children’s – CaCO3
  • Rennie (tablets) – CaCO3 MgCO3
  • Rolaids
    Rolaids
    Rolaids is a brand of antacid produced by McNeil Consumer Healthcare, a subsidiary of Johnson & Johnson. The brand was acquired from Pfizer Consumer Healthcare as part of a merger in 2006. It was invented by American chemist Irvine W. Grote in the late 1920s...

     – CaCO3 and Mg(OH)2
  • Tums
    Tums
    TUMS is an antacid made of sucrose and calcium carbonate manufactured by GlaxoSmithKline in St.Louis, Missouri, USA. It is a non-prescription drug and available at many retail stores, including drug stores, grocery stores and mass merchandisers. It provides relief from acid indigestion, heartburn,...

     – CaCO3
  • Mylanta
    Mylanta
    Mylanta is an over the counter antacid medication used for the treatment of acid reflux, heartburn, and gastroesophageal reflux disease .-Ingredients:...

     – contains Al(OH)3
  • Eno
    Eno (drug)
    Eno is the most global of GSK's gastrointestinal products. The fast-acting effervescent fruit salts, used as an antacid and reliever of bloatedness, was invented in the 1850s by James Crossley Eno...

  • Gelusil
    Gelusil
    Gelusil is an over-the counter drug that treats heartburn, acid indigestion and gas distributed by WellSpring Pharmaceutical Corporation. Its main ingredients are aluminum hydroxide, magnesium hydroxide and simethicone....

     (available in tablet and syrup form)

Additional information

Heartburn, reflux, indigestion, and sour stomach are a few of the common terms used to describe digestive upset. Self-diagnosis of indigestion does carry some risk because the causes can vary from a minor dietary indiscretion to a peptic ulcer. The pain and symptoms of gastric esophageal reflux disease, GERD or simply "reflux", may mimic those of a heart attack. Misdiagnosis can be fatal. A bleeding ulcer can be life threatening. GERD, and pre-ulcerative conditions in the stomach are treated much more aggressively since both, if untreated, could lead to esophageal or stomach cancer. It is primarily for this reason that the histamine-2 (H2) blockers including cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac), and the proton pump inhibitor (PPI) omeprazole (Prilosec) were made OTC. These drugs stop production of stomach acid and provide longer lasting relief but they do not neutralize any stomach acid already present in the stomach. For example, Pepcid Complete includes calcium carbonate in its formulation, allowing it a faster onset of action.

Interactions

Altered pH or complex formation may alter the bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...

 of other drugs, such as tetracycline and amphetamine
Amphetamine
Amphetamine or amfetamine is a psychostimulant drug of the phenethylamine class which produces increased wakefulness and focus in association with decreased fatigue and appetite.Brand names of medications that contain, or metabolize into, amphetamine include Adderall, Dexedrine, Dextrostat,...

. Urinary excretion of certain drugs may also be affected. Chelation of tetracycline with aluminium hydroxide can cause nausea, vomiting, and phosphate excretion, and cause phosphate deficiency.

Problems with reduced stomach acidity

Reduced stomach acidity may result in an impaired ability to digest
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....

 and absorb certain nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s, such as iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and the B vitamins. Since the low pH of the stomach normally kills ingested bacteria, antacids increase the vulnerability to infection. It could also result in reduced bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...

 of some drugs. For example, the bioavailability of ketoconazole
Ketoconazole
Ketoconazole is a synthetic antifungal drug used to prevent and treat fungal skin infections, especially in immunocompromised patients such as those with AIDS or those on chemotherapy. Ketoconazole is sold commercially as an anti-dandruff shampoo, topical cream, and oral tablet.Ketoconazole is...

 (antifungal) is reduced at high intragastric pH (low acid content).

See also

  • H2 antagonists
  • Brioschi (company) a manufacturer of an Italian Antacid.
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