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'[[Image:Antacid-L478.jpg|thumb|Antacid tablets]] An '''antacid''' is a substance which [[neutralization (chemistry)|neutralizes]] [[gastric acid|stomach acidity]]. ==Mechanism of action== Antacids either directly neutralize acidity, increasing the [[pH]], or reversibly reduce or block the secretion of acid by gastric cells to reduce acidity in the stomach. When gastric [[hydrochloric acid]] reaches the [[nerves]] in the gastrointestinal [[mucosa]], they [[Nociception|signal pain]] to the central nervous system. This happens when these nerves are exposed. In addition to the reduction of gastric acidity, antacids alsmnk,m.lk;.mn,,ngujknbghjksdfgh'''jm,n'''nnnn''''''Bold text'''''''''Bold text'''''''''Bold text'''nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbghhhhhhhhhhhhj,kkkkkkkkkkgvbgfggggggggggggggggggggggggggggggggggggggghbb jgytuuuuuuuuuuuuuiikl,.'''''''''''''''o alter the profile of prostaglandins produced by gastroduodenal mucosa and this may promote mucosal healing and be related to its therapeutic effect.<ref>{{cite journal | last=Preclik | first=G. | coauthors=Stange EF, Gerber K, Fetzer G, Horn H, Schneider A, Ditschuneit H. | year=1989 | volume=34 | issue=12 | pages=1860-4 | accessdate=2012-12-10 | doi=10.1007/BF01536703 | pmid=2598753 | title=Effect of antacid treatment on endogenous prostaglandin synthesis in human antral and duodenal mucosa. | journal=Digestive diseases and sciences }}</ref> ==Indications== [[Image:Old aluminum tablets.JPG|200px|left|thumb|Wyeth amphojel tablets of aluminum hydroxide.]] Antacids are taken by mouth to relieve [[heartburn]], the major symptom of [[gastroesophageal reflux disease]], or [[acid indigestion]]. Treatment with antacids alone is symptomatic and only justified for minor symptoms. The treatment of ulcers resulting from excessive acidity may require [[H2-receptor antagonist]]s or [[proton pump inhibitor]]s, and eradication of ''H. pylori''. ==Side effects== Excess [[calcium]] from supplements, fortified food and high-calcium diets, can cause [[milk-alkali syndrome]], 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]], [[alkalosis]], and [[hypercalcemia]]{{Clarify|calcemia or kalemia?|date=April 2010}}, 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&nbsp;mg daily, for prevention and treatment of [[osteoporosis]], 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]] 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.<ref>{{cite journal | last=Gabriely | first=I. | coauthors=Leu, J. P.; Barky, N. Korea | title=Clinical problem-solving, back to basics | journal=New England Journal of Medicine | date=May 1, 2008 | volume=358 | issue=18 | pages=1952&ndash;6 | accessdate=2008-05-29 | doi=10.1056/NEJMcps0706188 | pmid=18450607 }}</ref> Compounds containing calcium may also increase calcium output in the urine, which might be associated with [[kidney stones]].<ref>{{cite journal | last=Cooke | first=N. | coauthors=Teitelbaum, Ss; Avioli, L. V. | year=1978 | volume=138 | issue=6 | pages=1007&ndash;9 | accessdate=2008-05-29 | doi=10.1001/archinte.138.6.1007 | pmid=646554 | title=Antacid-induced osteomalacia and nephrolithiasis | journal=Archives of Internal Medicine }}</ref> Calcium salts may cause [[constipation]]. Other adverse effects from antacids include: *''[[Carbonate]]'' and ''[[bicarbonate]]'': regular high doses may cause [[alkalosis]], 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]] and [[osteomalacia]]. Although [[aluminium]] has a low gastrointestinal absorption, accumulation may occur mainly in the presence of [[renal insufficiency]]. Aluminium-containing drugs often cause [[constipation]] and are neurotoxic. Aluminium-containing drugs are contraindicated in pregnancy. *''[[Magnesium hydroxide]]'': has [[laxative]] properties. Magnesium may accumulate in patients with [[renal failure]] leading to [[hypermagnesemia]], 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 the individual, and on 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]] – NaHCO₃ and/or KHCO₃ *Andrews Antacid – CaCO₃ MgCO₃ *[[Brioschi (company)|Brioschi]] – NaHCO₃ *[[List of Wal-Mart brands#Others|Equate]] – Al(OH)₃ and Mg(OH)₂ *[[Maalox]] (liquid) – Al(OH)₃ and Mg(OH)₂ *Maalox (tablet) – CaCO₃ *[[Milk of Magnesia]] – Mg(OH)₂ *[[Bismuth subsalicylate|Pepto-Bismol]] – C₇H₅BiO₄ *Pepto-Bismol Children’s – CaCO₃ *Rennie (tablets) – CaCO₃ MgCO₃ *[[Rolaids]] – CaCO₃ and Mg(OH)₂ *[[Tums]] – [[Calcium carbonate|CaCO₃]] *[[Mylanta]] – contains Al(OH)₃ *[[Eno (drug)|Eno]] - NaHCO₃, Citric acid, Na₂CO₃ *[[Gelusil]] (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 [[gastro-oesophageal 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 oesophageal or stomach cancer. It is primarily for this reason that the histamine [[H2 antagonist]]s including [[cimetidine]] (Tagamet), [[famotidine]] (Pepcid), and [[ranitidine]] (Zantac), and the [[proton pump inhibitor]] (PPI) [[omeprazole]] (Prilosec) were made OTC{{Citation needed|date=October 2011}}. 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]] of other drugs, such as [[tetracycline]] and [[amphetamine]]. Urinary excretion of certain drugs may also be affected. Chelation of tetracycline with aluminium hydroxide can cause nausea, vomiting, and phosphate excretion, resulting in phosphate deficiency. ==Problems with reduced stomach acidity== Antacid preparations, by suppressing acid mediated break down of proteins, lead to an elevated risk of developing food and drug allergies. This happens due to undigested proteins passing into the gastrointestinal tract. It is unclear whether this risk occurs only with long-term use or with short-term use as well.<ref name="pmid21121928">{{cite journal |author=Pali-Schöll I, Jensen-Jarolim E |title=Anti-acid medication as a risk factor for food allergy |journal=Allergy |volume=66 |issue=4 |pages=469–77 |year=2011 |month=April |pmid=21121928 |doi=10.1111/j.1398-9995.2010.02511.x |url=}}</ref> Reduced stomach acidity may result in an impaired ability to [[Digestion|digest]] and absorb certain [[nutrient]]s, such as [[iron]] and the [[vitamin B|B vitamins]]{{fact|date=October 2012}}. Since the low pH of the stomach normally kills ingested bacteria, antacids increase the vulnerability to infection{{fact|date=October 2012}}. It could also result in reduced [[bioavailability]] of some drugs. For example, the bioavailability of [[ketoconazole]] (antifungal) is reduced at high intragastric pH (low acid content).{{fact|date=October 2012}} ==See also== *[[H2 antagonist|H₂ antagonists]] *[[Hydrotalcite]] *[[Layered double hydroxides]] ==References== {{Refimprove|article|date=December 2007}} {{Reflist}} {{Wiktionary|antacid}} {{Major Drug Groups}} {{Antacids}} [[Category:Antacids| ]] [[ar:مضاد الحموضة]] [[ca:Antiàcid]] [[cs:Antacida]] [[de:Antazidum]] [[es:Antiácido]] [[eu:Antiazido]] [[fr:Antiacide]] [[hr:Antacidi]] [[id:Antasid]] [[it:Antiacido]] [[kk:Антацид]] [[ml:അന്റാസിഡുകൾ]] [[nl:Antacidum]] [[ja:制酸薬]] [[pt:Antiácido]] [[ru:Антациды]] [[simple:Antacid]] [[sk:Antacidum]] [[sl:Antacid]] [[sr:Антацид]] [[sh:Antacid]] [[fi:Antasidi]] [[sv:Antacida]] [[tl:Antasido]] [[th:ยาลดกรด]] [[tr:Antiasitler]] [[uk:Антациди]] [[wuu:抗酸剂]] [[zh:抗酸药]]'