View source for Antacid

{{Short description|Substance that relieves stomach problems}}
{{About|the medication used to relieve heartburn|the acid produced by ants, known in many languages as "ant acid"|Formic acid}}
{{Distinguish|text=acid suppression therapy with [[proton-pump inhibitor|PPIs]] or [[H2 receptor antagonist|H2RAs]], which reduces acid production}}
{{Use dmy dates|date=January 2024}}
[[Image:Antacid-L478.jpg|thumb|[[Calcium carbonate]] antacid tablets]]

An '''antacid''' is a substance which [[neutralization (chemistry)|neutralizes]] [[gastric acid|stomach acidity]] and is used to relieve [[heartburn]], [[indigestion]], or an upset stomach.<ref name="Overviewcookie">{{Cite book|title=Dyspepsia and Gastro-Oesophageal Reflux Disease: Investigation and Management of Dyspepsia, Symptoms Suggestive of Gastro-Oesophageal Reflux Disease, or Both|last=Internal Clinical Guidelines Team. (UK)|date=2014|publisher=National Institute for Health and Care Excellence (UK)|series=National Institute for Health and Care Excellence: Clinical Guidelines|location=London|pmid=25340236}}</ref> Some antacids have been used in the treatment of [[constipation]] and [[diarrhea]].<ref name="pmid30252305">{{cite book | vauthors = Salisbury BH, Terrell JM | chapter = Antacids | title = StatPearls | date = 2020 | pmid = 30252305 | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK526049/ | access-date = 24 November 2020 | publisher = StatPearls Publishing | url-status = live | place = Treasure Island (FL) | archive-url = https://web.archive.org/web/20211105005803/https://www.ncbi.nlm.nih.gov/books/NBK526049/ | archive-date = 5 November 2021 }}</ref> Marketed antacids contain [[Salt (chemistry)|salts]] of [[aluminium]], [[calcium]], [[magnesium]], or [[sodium]].<ref name="pmid30252305" /> Some preparations contain a combination of two [[Salt (chemistry)|salts]], such as [[magnesium carbonate]] and [[aluminium hydroxide]] (e.g., [[hydrotalcite]]).<ref>{{Cite web|title=Aluminium hydroxide and magnesium carbonate Uses, Side Effects & Warnings|url=https://www.drugs.com/mtm/aluminum-hydroxide-and-magnesium-carbonate.html|access-date=24 November 2020|website=Drugs.com|archive-date=20 May 2021|archive-url=https://web.archive.org/web/20210520014232/https://www.drugs.com/mtm/aluminum-hydroxide-and-magnesium-carbonate.html|url-status=live}}</ref>

==Medical uses==
Antacids are available [[over the counter]] and are taken by mouth to quickly relieve occasional [[heartburn]], the major symptom of [[gastroesophageal reflux disease]] and [[indigestion]]. Treatment with antacids alone is [[Symptomatic treatment|symptomatic]] and only justified for minor symptoms.<ref name=AHRQ>{{cite web | publisher = U.S. Department of Health & Human Services. Agency for Healthcare Research and Quality | date = 23 September 2011 | url = http://effectivehealthcare.ahrq.gov/index.cfm/search-for-guides-reviews-and-reports/?pageaction=displayproduct&productID=756 | title = Consumer Summary – Treatment Options for GERD or Acid Reflux Disease: A Review of the Research for Adults | archive-url = https://web.archive.org/web/20141011121858/http://effectivehealthcare.ahrq.gov/index.cfm/search-for-guides-reviews-and-reports/?productid=756&pageaction=displayproduct | archive-date = 11 October 2014 }}</ref> Alternative uses for antacids include constipation, diarrhea, hyperphosphatemia, and urinary alkalization.<ref name="pmid30252305" /> Some antacids are also used as an [[Adjuvant therapy|adjunct]] to pancreatic enzyme replacement therapy in the treatment of [[Exocrine pancreatic insufficiency|pancreatic insufficiency]].<ref>{{cite journal | vauthors = Graham DY | title = Pancreatic enzyme replacement: the effect of antacids or cimetidine | journal = Digestive Diseases and Sciences | volume = 27 | issue = 6 | pages = 485–490 | date = June 1982 | pmid = 6282548 | doi = 10.1007/BF01296725 | s2cid = 10640940 }}</ref>

Non-particulate antacids ([[Trisodium citrate|sodium citrate]]) 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 one hour of surgery to be the most effective.<ref name="pmid28045707">{{cite journal | vauthors = Apfelbaum JL, Agarkar M, Connis RT, Coté CJ, Nickinovich DJ, Warner MA | collaboration = American Society of Anesthesiologists Committee on Standards and Practice Parameters | title = Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures: An Updated Report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration | journal = Anesthesiology | volume = 126 | issue = 3 | pages = 376–393 | date = March 2017 | pmid = 28045707 | doi = 10.1097/ALN.0000000000001452 }}</ref>

==Side effects==
Conventional effervescent tablets contain a significant amount of [[sodium]] and are associated with increased risk of adverse cardiovascular events according to a 2013 study.<ref>{{cite journal | vauthors = George J, Majeed W, Mackenzie IS, Macdonald TM, Wei L | title = Association between cardiovascular events and sodium-containing effervescent, dispersible, and soluble drugs: nested case-control study | journal = BMJ | volume = 347 | article-number = f6954 | date = November 2013 | pmid = 24284017 | pmc = 3898660 | doi = 10.1136/bmj.f6954 | doi-access = free }}</ref> Alternative sodium-free formulations containing [[Magnesium|magnesium salts]] may cause diarrhea, whereas those containing [[calcium]] or [[aluminium]] may cause [[constipation]].<ref name="Garg_2022">{{cite journal | vauthors = Garg V, Narang P, Taneja R | title = Antacids revisited: review on contemporary facts and relevance for self-management | journal = The Journal of International Medical Research | volume = 50 | issue = 3 | date = March 2022 | article-number = 03000605221086457 | pmid = 35343261 | pmc = 8966100 | doi = 10.1177/03000605221086457 }}</ref>{{Rp|location=Table 2}} Long-term use of antacids containing [[aluminium]] may increase the risk of developing [[osteoporosis]].<ref name="MedlinePlus">{{cite web | publisher = U.S. Department of Health and Human Services, National Institutes of Health, U.S. National Library of Medicine | date = 7 November 2014 | url = https://www.medlineplus.gov/ency/patientinstructions/000198.htm | work = Medline Plus | title = Taking Antacids | url-status = live | archive-url = https://web.archive.org/web/20160705125204/https://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000198.htm |archive-date=5 July 2016 }}</ref> [[In vitro]] 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.<ref>{{cite journal | vauthors = Texter EC | title = A critical look at the clinical use of antacids in acid-peptic disease and gastric acid rebound | journal = The American Journal of Gastroenterology | volume = 84 | issue = 2 | pages = 97–108 | date = February 1989 | pmid = 2644821 }}</ref><ref>{{cite journal | vauthors = Hade JE, Spiro HM | title = Calcium and acid rebound: a reappraisal | journal = Journal of Clinical Gastroenterology | volume = 15 | issue = 1 | pages = 37–44 | date = July 1992 | pmid = 1500660 | doi = 10.1097/00004836-199207000-00010 | s2cid = 10897187 }}</ref>

==Properties of antacids==
When an excess amount of acid is produced in the [[stomach]], the natural [[Mucous membrane|mucous barrier]] that protects the lining of the stomach can degrade, leading to [[pain]] and [[irritation]].<ref>{{cite journal | vauthors = McColl KE | title = The elegance of the gastric mucosal barrier: designed by nature for nature | journal =   Gut| volume = 61 | issue = 6 | pages = 787–788 | date = October 2011 | doi = 10.1136/gutjnl-2011-301612| pmid = 22147513 }}</ref> There is also potential for the development of [[Gastroesophageal reflux disease|acid reflux]], which can cause pain and damage to the [[esophagus]].<ref>{{Cite web |date=2017-06-01 |title=When does long-term acid reflux become a serious issue? |url=https://www.health.harvard.edu/digestive-health/when-does-long-term-acid-reflux-become-a-serious-issue |access-date=2025-08-14 |website=Harvard Health |language=en}}</ref> Antacids contain [[alkaline]] ions that [[Neutralization (chemistry)|chemically neutralize]] stomach [[gastric acid]], reducing damage to the stomach lining and [[esophagus]], and relieving pain.<ref name="Overviewcookie" /> Some antacids also inhibit [[pepsin]], an [[enzyme]] that can damage the [[esophagus]] in [[Acid Reflux|acid reflux]].<ref name="pmid30252305"/><ref>{{cite journal | vauthors = Bardhan KD, Strugala V, Dettmar PW | title = Reflux revisited: advancing the role of pepsin | journal = International Journal of Otolaryngology | volume = 2012 | article-number = 646901 | date = 2012 | pmid = 22242022 | pmc = 3216344 | doi = 10.1155/2012/646901 | doi-access = free }}</ref>

Antacids do not directly inhibit acid [[secretion]], and thus are distinct from acid-reducing drugs like [[H2 antagonist|H<sub>2</sub>-receptor antagonist]]s or [[proton pump inhibitor]]s.<ref name="AHRQ" /> Antacids do not kill the bacterium, ''[[Helicobacter pylori]]'', which causes most [[gastric ulcer|ulcers]].<ref name="AHRQ" />

==Types==
Antacids are mainly classified into two categories: 

* Systemic (absorbable) antacids: They are [[water soluble]] and systemically absorbed and pass into the [[bloodstream]].  e.g. [[sodium bicarbonate]] or [[sodium citrate]]
* Non-systemic (non-absorbable) antacids: They are [[insoluble]] and not absorbed into systemic circulation. They only act in the [[stomach]] e.g. [[magnesium carbonate]] or [[calcium carbonate]]<ref>MrlabTest - Antacids. URL: [https://www.mrlabtest.com/medication/antacids.htm https://www.mrlabtest.com/medication/antacids.htm]. Accessed on: November 27, 2024.</ref> 

== Interactions ==
[[File:Basic structure of tetracycline chelating a metal.svg|thumb|Structural depiction of tetracycline metal chelation, where 'M' is a metal such as those found in antacids]]
Antacids are known to [[Drug interaction|interact]] with several [[Oral administration|oral medications]], including [[Quinolone antibiotic|fluoroquinolone]] and [[tetracycline]] [[antibiotic]]s, [[iron]], [[itraconazole]], and [[prednisone]].<ref name="Ogawa_2011">{{cite journal | vauthors = Ogawa R, Echizen H | title = Clinically significant drug interactions with antacids: an update | journal = Drugs | volume = 71 | issue = 14 | pages = 1839–1864 | date = October 2011 | pmid = 21942976 | doi = 10.2165/11593990-000000000-00000 | s2cid = 36875514 }}</ref> Metal [[chelation]] is responsible for some of these interactions (e.g. [[fluoroquinolones]], [[tetracyclines]]), leading to decreased absorption of the chelated drug. Some interactions may be due to the [[pH]] increase observed in the [[stomach]] following antacid [[ingestion]], leading to increased absorption of weak acids, and decreased absorption of weak bases.<ref>{{Cite journal |last=Patel |first=Divya |last2=Bertz |first2=Richard |last3=Ren |first3=Song |last4=Boulton |first4=David W. |last5=Någård |first5=Mats |date=April 2020 |title=A Systematic Review of Gastric Acid-Reducing Agent-Mediated Drug-Drug Interactions with Orally Administered Medications |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC7109143/ |journal=Clinical Pharmacokinetics |volume=59 |issue=4 |pages=447–462 |doi=10.1007/s40262-019-00844-3 |issn=1179-1926 |pmc=7109143 |pmid=31788764}}</ref> Antacids also cause an increase in [[pH]] of the [[urine]] (alkalization), which may cause increased [[blood]] concentrations of weak bases, and increased [[excretion]] of weak acids.<ref name="Patel_2020">{{cite journal | vauthors = Patel D, Bertz R, Ren S, Boulton DW, Någård M | title = A Systematic Review of Gastric Acid-Reducing Agent-Mediated Drug-Drug Interactions with Orally Administered Medications | journal = Clinical Pharmacokinetics | volume = 59 | issue = 4 | pages = 447–462 | date = April 2020 | pmid = 31788764 | pmc = 7109143 | doi = 10.1007/s40262-019-00844-3 }}</ref>

A proposed method to mitigate the effects of [[stomach]] acidity and [[chelation]] on drug absorption is to space out the administration of antacids with interacting [[medication]]s by at least two hours,<ref>{{Cite book |publisher=Australian Medicines Handbook Pty |title=Australian Medicines Handbook 2022 |year=2022 |isbn=978-0-6485158-6-9 |location=Adelaide, SA}}</ref> however this method has not been well studied for drugs affected by [[Urine|urine alkalization]].<ref name="Ogawa_2011" />

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|pH sensitive]].<ref name="Patel_2020" />

==Formulations==
Antacids may be formulated with other [[active pharmaceutical ingredient|active ingredients]] such as [[simethicone]] to control [[Flatulence|gas]], or [[alginic acid]] to act as a physical barrier to acid.<ref>{{cite web | publisher = International Foundation for Functional Gastrointestinal Disorders, Inc. (IFFGD) | url = http://www.iffgd.org/site/manage-your-health/diet-treatments/antacids | title = Antacids | archive-url = https://web.archive.org/web/20160506182546/http://www.iffgd.org/site/manage-your-health/diet-treatments/antacids | archive-date = 6 May 2016 | work = IFFGD Publication #520 | vauthors = Thompson WG | date = 12 September 2014 }}</ref>

=== Liquids ===
[[File:Bismuth Subsalicylate Bottle.png|thumb|150px|A bottle of liquid antacid containing [[bismuth subsalicylate]] as the active ingredient]]
Several liquid antacid preparations are [[marketed]]. Common liquid preparations include [[Magnesium hydroxide|milk of magnesia]] and magnesium/aluminium [[combination]]s. 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.<ref>{{cite journal | vauthors = Barnett CC, Richardson CT | title = In vivo and in vitro evaluation of magnesium-aluminium hydroxide antacid tablets and liquid | journal = Digestive Diseases and Sciences | volume = 30 | issue = 11 | pages = 1049–1052 | date = November 1985 | pmid = 4053915 | doi = 10.1007/BF01315602 | s2cid = 8133980 }}</ref>

=== Tablets ===

==== Chewable tablets ====
[[Chewable tablet|Chewable]] tablets are one of the most common forms of antacids, most frequently made from [[carbonate]] or [[hydroxide]] [[Salt (chemistry)|salts]], and are readily available over the counter. Upon reaching the [[stomach]], the powdered antacid salts bind to [[hydronium]] (H<sup>+</sup>) ions, producing [[chloride]] salts, carbon dioxide, and water. This process reduces the concentration of H<sup>+</sup> ions in the stomach, raising the pH and neutralizing the acid.<ref name="Garg_2022" />{{Rp|location=Figure 1}} Common carbonate salts available in tablet form include those of calcium, magnesium, aluminium, and sodium.<ref name="Ogawa_2011" />

Some common American brands are [[Tums]], Gaviscon chewable tablets, and [[Maalox]] chewable tablets.<ref>{{Cite web |title=Maalox Antacid Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing |url=https://www.webmd.com/drugs/2/drug-19216/maalox-antacid-oral/details |access-date=24 June 2022 |website=WebMD |archive-date=24 June 2022 |archive-url=https://web.archive.org/web/20220624114050/https://www.webmd.com/drugs/2/drug-19216/maalox-antacid-oral/details |url-status=live }}</ref>

==== Effervescent tablets ====
Effervescent tablets are tablets which are designed to dissolve in [[water]], and then release [[carbon dioxide]].<ref>{{cite news| vauthors = Dubogrey I |title=Putting the Fizz into Formulation|url=http://www.samedanltd.com/magazine/11/issue/204/article/3622|work=European Pharmaceutical Contractor|issue=Autumn|date=2013|access-date=17 April 2017|archive-date=28 August 2021|archive-url=https://web.archive.org/web/20210828151212/http://www.samedanltd.com/magazine/11/issue/204/article/3622}}</ref><ref>{{cite web | url = http://www.newdruginfo.com/pharmacopeia/bp2003/British%20Pharmacopoeia%20Volume%20III/Monographs/Formulated%20Preparations%20Genearal%20Monographs/TABLETS.htm | title = Tablets | work = British Pharmacopeia | date = 2003 | archive-url = https://web.archive.org/web/20130103012204/http://www.newdruginfo.com/pharmacopeia/bp2003/British%20Pharmacopoeia%20Volume%20III/Monographs/Formulated%20Preparations%20Genearal%20Monographs/TABLETS.htm | archive-date = 3 January 2013 }}</ref><ref>{{cite book|title=International Pharmacopoeia 2006|url=https://archive.org/details/bub_gb_s_sBKJNf184C|access-date=1 July 2013|year=2006|publisher=World Health Organization|isbn=978-92-4-156301-7|pages=[https://archive.org/details/bub_gb_s_sBKJNf184C/page/n993 966]}}</ref> Common ingredients include [[citric acid]] and [[sodium bicarbonate]], which react when in contact with water to produce [[carbon dioxide]]. Effervescent antacids may also contain [[aspirin]],<ref>{{cite web|url=http://www.alkaseltzer.ie/en/about-alka-seltzer/|title=Alka Seltzer Directions of use, Sodium & Aspirin content – Alka Seltzer relief from Headaches, Migraine & Upset stomach|work=alkaseltzer.ie|access-date=17 April 2017|archive-url=https://web.archive.org/web/20150429145428/http://www.alkaseltzer.ie/en/about-alka-seltzer/|archive-date=29 April 2015}}</ref> [[sodium carbonate]], or [[tartaric acid]].<ref name=Blair>{{cite encyclopedia | vauthors = Blair GT, DeFraties JJ | title = Kirk-Othmer Encyclopedia of Chemical Technology | encyclopedia = Kirk Othmer Encyclopedia of Chemical Technology | year = 2000 | pages = 1–19 | doi = 10.1002/0471238961.0825041802120109.a01 | chapter = Hydroxy Dicarboxylic Acids | isbn = 978-0-471-23896-6 }}</ref> Those containing aspirin may cause further [[gastric]] irritation and [[ulceration]] due to [[aspirin]]'s effects on the [[Mucus|mucous]] membrane of the [[stomach]].<ref>{{cite journal | vauthors = Graham DY, Smith JL | title = Aspirin and the stomach | journal = Annals of Internal Medicine | volume = 104 | issue = 3 | pages = 390–398 | date = March 1986 | pmid = 3511824 | doi = 10.7326/0003-4819-104-3-390 }}</ref>

== Brand names ==
Some [[brand]]s include [[Alka-Seltzer]], Gaviscon, [[Tums]], Gelusil and [[Eno (drug)|Eno]].<ref>{{Cite web |date=30 March 2023 |title=Which OTC Meds Treat Heartburn? |url=https://www.webmd.com/heartburn-gerd/treating-heartburn-over-counter-medicine |access-date=8 January 2024 |website=WebMD}}</ref><ref>{{cite web |title=Eno – Summary of Product Characteristics at eMC |url=https://www.medicines.org.uk/emc/medicine/21528 |access-date=2 September 2016 |website=Electronic Medicines Compendium |quote=Last updated 1 January 2016}}</ref><ref>{{cite web |title=Gelusil - Uses, Side Effects, and More |url=https://www.webmd.com/drugs/2/drug-14836/gelusil-antacid-and-anti-gas-oral/details |access-date=27 February 2024}}</ref>

== References ==
{{Reflist}}

== External links ==
* {{Wiktionary inline|antacid}}

{{Antacids}}
{{Major Drug Groups}}
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[[Category:Antacids| ]]