An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach.[1] Some antacids have been used in the treatment of constipation and diarrhea.[2] Marketed antacids contain salts of aluminum, calcium, magnesium, or sodium.[2] Some preparations contain a combination of two salts, such as magnesium carbonate and aluminium hydroxide (e.g. hydrotalcite).[3]

Calcium carbonate antacid tablets

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 and only justified for minor symptoms.[4] Alternative uses for antacids include constipation, diarrhea, hyperphosphatemia, and urinary alkalization.[5] Some antacids are also used as an adjunct to pancreatic enzyme replacement therapy in the treatment of pancreatic insufficiency.[6]

Non-particulate antacids (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 1 hour of surgery to be the most effective.[7]

Side effects

Conventional effervescent tablets contain a significant amount of sodium and are associated with increased odds of adverse cardiovascular events according to an 2013 study.[8] Alternative sodium-free formulations containing magnesium salts may cause diarrhea, whereas those containing calcium or aluminum may cause constipation. Rarely, long-term use of calcium carbonate may cause kidney stones. Long-term use of antacids containing aluminum may increase the risk of developing osteoporosis.[9] 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.[10][11]

Properties of antacids

When an excess amount of acid is produced in the stomach, the natural mucous barrier that protects the lining of the stomach can degrade, leading to pain and irritation. There is also potential for the development of acid reflux, which can cause pain and damage to the esophagus. Antacids contain alkaline ions that chemically neutralize stomach gastric acid, reducing damage to the stomach lining and esophagus, and relieving pain.[1] Some antacids also inhibit pepsin, an enzyme that can damage the esophagus in acid reflux.[5][12]

Antacids do not directly inhibit acid secretion, and thus are distinct from acid-reducing drugs like H2-receptor antagonists or proton pump inhibitors.[4] Antacids do not kill the bacteria Helicobacter pylori, which causes most ulcers.[4]


Structural depiction of tetracycline metal chelation, where 'M' is a metal such as those found in antacids

Antacids are known to interact with several oral medications, including fluoroquinolone and tetracycline antibiotics, iron, itraconazole, and prednisone.[13] 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. 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.[14]

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 medications, however this method has not been well studied for drugs affected by urine alkalization.[13]

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.[14]


Antacids may be formulated with other active ingredients such as simethicone to control gas, or alginic acid to act as a physical barrier to acid.[15]


Several liquid antacid preparations are marketed. Common liquid preparations include milk of magnesia 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.[16] Common brands include Pepto-Bismol and Gaviscon.

Chewable tablets

Chewable tablets are one of the most common forms of antacids, and are readily available over the counter. Upon reaching the stomach, 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.[13]

Some common brand are Tums, Gaviscon chewable tablets and Maalox chewable tablets.[17]

Effervescent tablets

Effervescent tablets are tablets which are designed to dissolve in water, and then release carbon dioxide.[18][19][20] 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,[21] sodium carbonate, or tartaric acid.[22] Those containing aspirin may cause further gastric irritation and ulceration due to aspirin's effects on the mucous membrane of the stomach.[23]

Common brands include Alka-Seltzer, Gaviscon, and Eno.


  1. Internal Clinical Guidelines Team. (UK) (2014). Dyspepsia and Gastro-Oesophageal Reflux Disease: Investigation and Management of Dyspepsia, Symptoms Suggestive of Gastro-Oesophageal Reflux Disease, or Both. National Institute for Health and Care Excellence: Clinical Guidelines. London: National Institute for Health and Care Excellence (UK). PMID 25340236.
  2. Salisbury, Blake H.; Terrell, Jamie M. (2020), "Antacids", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30252305, retrieved 24 November 2020
  3. "Aluminum hydroxide and magnesium carbonate Uses, Side Effects & Warnings". Retrieved 24 November 2020.
  4. U.S. Department of Health & Human Services. Agency for Healthcare Research and Quality 23 September 2011 Consumer Summary – Treatment Options for GERD or Acid Reflux Disease: A Review of the Research for Adults Archived 11 October 2014 at the Wayback Machine
  5. Salisbury, Blake H.; Terrell, Jamie M. (2020), "Antacids", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30252305, retrieved 23 December 2020
  6. Graham, D. Y. (1982). "Pancreatic enzyme replacement: the effect of antacids or cimetidine". Digestive Diseases and Sciences. 27 (6): 485–490. doi:10.1007/BF01296725. ISSN 0163-2116. PMID 6282548. S2CID 10640940.
  7. 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. Anesthesiology. 2017 March; 126(3).
  8. George, J; Majeed, W; Mackenzie, IS; Macdonald, TM; Wei, L (26 November 2013). "Association between cardiovascular events and sodium-containing effervescent, dispersible, and soluble drugs: nested case-control study". BMJ (Clinical Research Ed.). 347: f6954. doi:10.1136/bmj.f6954. PMC 3898660. PMID 24284017.
  9. U.S. Department of Health and Human Services, National Institutes of Health, U.S. National Library of Medicine. Page last updated: 7 November 2014 Medline Plus: Taking Antacids
  10. Texter, E. C. (1989). "A critical look at the clinical use of antacids in acid-peptic disease and gastric acid rebound". The American Journal of Gastroenterology. 84 (2): 97–108. ISSN 0002-9270. PMID 2644821.
  11. Hade, J. E.; Spiro, H. (1992). "Calcium and acid rebound: a reappraisal". Journal of Clinical Gastroenterology. 15 (1): 37–44. doi:10.1097/00004836-199207000-00010. PMID 1500660. S2CID 10897187.
  12. Bardhan, Karna Dev; Strugala, Vicki; Dettmar, Peter W. (2012). "Reflux Revisited: Advancing the Role of Pepsin". International Journal of Otolaryngology. 2012: 646901. doi:10.1155/2012/646901. ISSN 1687-9201. PMC 3216344. PMID 22242022.
  13. Ogawa, Ryuichi; Echizen, Hirotoshi (2011). "Clinically Significant Drug Interactions with Antacids". Drugs. 71 (14): 1839–1864. doi:10.2165/11593990-000000000-00000. ISSN 0012-6667. PMID 21942976. S2CID 36875514.
  14. Patel, Divya; Bertz, Richard; Ren, Song; Boulton, David W.; Någård, Mats (2020). "A Systematic Review of Gastric Acid-Reducing Agent-Mediated Drug–Drug Interactions with Orally Administered Medications". Clinical Pharmacokinetics. 59 (4): 447–462. doi:10.1007/s40262-019-00844-3. ISSN 0312-5963. PMC 7109143. PMID 31788764.
  15. IFFGD. Antacids Adapted from IFFGD Publication #520 by W. Grant Thompson. Last modified on 12 September 2014
  16. Barnett, C. C.; Richardson, C. T. (1985). "In vivo and in vitro evaluation of magnesium-aluminum hydroxide antacid tablets and liquid". Digestive Diseases and Sciences. 30 (11): 1049–1052. doi:10.1007/BF01315602. ISSN 0163-2116. PMID 4053915. S2CID 8133980.
  17. "Maalox Antacid Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing - WebMD". Retrieved 24 June 2022.
  18. Dubogrey, Ilya (2013). "Putting the Fizz into Formulation". European Pharmaceutical Contractor. No. Autumn.
  19. British Pharmacopeia 2003
  20. International Pharmacopoeia 2006. World Health Organization. 2006. pp. 966. ISBN 978-92-4-156301-7. Retrieved 1 July 2013.
  21. "Alka Seltzer Directions of use, Sodium & Aspirin content - Alka Seltzer relief from Headaches, Migraine & Upset stomach". Archived from the original on 29 April 2015. Retrieved 17 April 2017.
  22. Blair, G. T.; DeFraties, J. J. (2000). "Hydroxy Dicarboxylic Acids". Kirk-Othmer Encyclopedia of Chemical Technology. Kirk Othmer Encyclopedia of Chemical Technology. pp. 1–19. doi:10.1002/0471238961.0825041802120109.a01. ISBN 978-0471238966.
  23. Graham, David Y.; Smith, J. Lacey (1 March 1986). "Aspirin and the Stomach". Annals of Internal Medicine. 104 (3): 390–398. doi:10.7326/0003-4819-104-3-390. ISSN 0003-4819. PMID 3511824.
  • The dictionary definition of antacid at Wiktionary
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