Magnesium hydroxide 187.5mg tablets
Magnesium hydroxide is an inorganic compound.
Safety information for pregnancy and breastfeeding
Breastfeeding
Always consult your doctor or midwife before taking any medicine during pregnancy or while breastfeeding. Source: DrugBank (CC BY-NC 4.0).
Official documents, adverse reaction reporting, and safety monitoring
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Safety monitoring data
Yellow Card reports
The MHRA Yellow Card scheme collects reports of suspected side effects from healthcare professionals and patients. View the Drug Analysis Profile (iDAP) for real-world adverse reaction data.
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Suspected adverse reactions reported for Magnesium hydroxide
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Submit a Yellow Card report to the MHRA
Data from the MHRA Yellow Card scheme. A reported reaction does not necessarily mean the medicine caused it. Contains public sector information licensed under the Open Government Licence v3.0.
EudraVigilance
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Suspected adverse reactions reported for Magnesium hydroxide
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EudraVigilance data is published by the European Medicines Agency (EMA). A suspected adverse reaction is not necessarily caused by the medicine.
1 branded products available
WHO defined daily dose (DDD)
3 gram
Not a recommended dose. The DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults. It is a statistical measure used for research and comparison purposes only.
Source: WHO Collaborating Centre for Drug Statistics Methodology, distributed via the NHS dm+d supplementary BNF/ATC mapping files (NHSBSA). Contains public sector information licensed under the Open Government Licence v3.0.
Therapeutically similar medicines
Similarity is based on WHO Anatomical Therapeutic Chemical (ATC) classification and on a factual NHS dm+d therapeutic-grouping code prefix. Source data: NHS dm+d via TRUD (OGL v3.0), WHO ATC/DDD Index.
NHS prescribing volume and spending trends
Guidelines from the National Institute for Health and Care Excellence
NICE clinical guidance(1)
Source: National Institute for Health and Care Excellence (NICE). Contains public sector information licensed under the Open Government Licence v3.0.
Check stock at pharmacies and supply information
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Supply & safety information
Official UK regulator monitoring and safety alerts
Pharmacy links redirect to the retailer's own search and do not represent real-time stock levels. Shortage and safety information sourced from MHRA drug safety updates (gov.uk, Crown Copyright under OGL v3.0).
Codes for healthcare professionals and prescribing systems
These codes are used by healthcare IT systems and prescribers to identify this medicine.
NHS UK identifiers
Browse tools
SNOMED CT and dm+d codes from NHS TRUD (Technology Reference data Update Distribution), licensed under the Open Government Licence v3.0. BNF code shown is the factual mapping value distributed by NHS Business Services Authority (NHSBSA) in the dm+d supplementary file under OGL v3.0; it is not affiliated with, nor licensed from, the publishers of the British National Formulary. ATC codes from the WHO Collaborating Centre for Drug Statistics Methodology (whocc.no).
Active and completed clinical studies from ClinicalTrials.gov
Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine (NLM), National Institutes of Health (NIH). Data accessed via ClinicalTrials.gov API v2. Trial information is provided for research purposes and does not constitute medical advice.
Academic studies and reviews for this medicine's active substance
Showing the 50 most relevant studies.
Reviews & meta-analyses: 5 · Randomised trials: 3 · 1962–2026
Showing the 50 most relevant studies, sorted by most relevant.
Lian Guo, Wei Wu, Yongfeng Zhou, et al.
Journal of Material Science and Technology, 2018
Zhao-Qi Zhang, Yong-Xin Yang, Jing-an Li, et al.
Bioactive Materials, 2021
Feng Peng, Hua Li, Donghui Wang, et al.
ACS applied materials & interfaces, 2016
Giulia Balducci, Laura Bravo Diaz, Duncan H. Gregory
CrystEngComm, 2017
Liang Wu, Danni Yang, Gen Zhang, et al.
Applied Surface Science, 2018
Kistemaker KRJ, de Graeff A, Crul M, et al.
2023
- Neoplasms
- Opioid-Induced Constipation
- Constipation
M.S. Yong, Meng Tang, Liangliang Sun, et al.
Nature Sustainability, 2024
Nate-Anong B, Khorana J, Chantakhow S, et al.
2025
- Constipation
- Magnesium Hydroxide
- Polyethylene Glycols
Mohini Sain, Sung Heum PARK, F. Suhara, et al.
Polymer Degradation and Stability, 2003
Yi Ding, Guangtao Zhang, Hao Wu, et al.
Chemistry of Materials, 2001
Sources: aggregated from Europe PMC (EMBL-EBI), OpenAlex, Crossref, PubMed and other open scholarly databases. Retracted articles are excluded. Study information is provided for research purposes and does not constitute medical advice.
Pharmacology and chemical data from DrugBank
Key facts
Drug status
Approved
Major interactions
70 found
Half-life
Not available
Mechanism
The suspension of magnesium hydroxide is ingested and enters the stomach.
Food interactions
None known
Human targets
None mapped
Data: DrugBank · CC BY-NC 4.0
Pharmacokinetics at a glance
Absorption
15%
Half-life
Protein binding
Volume of distribution
Metabolism
15%
Elimination
50%
Clearance
Pharmacokinetic data: DrugBank · CC BY-NC 4.0
Additionally, magnesium hydroxide has smoke suppressing and flame retardant properties and is thus used commercially as a fire retardant.
It can also be used topically as a deodorant or for the relief of canker sores (aphthous ulcers).
As an antacid, it is used for the temporary relief of heartburn, upset stomach, sour stomach or acid indigestion.
As a laxative, it is used for the relief of occasional constipation by promoting bowel movements for 30 minutes and up to 6 hours.
Known interactions with other medications. Always consult a healthcare professional.
Showing 50 of 1302 interactions
Common side effects include drowsiness or flushing (warmth, redness or tingly feeling).
Daily use of magnesium hydroxide can result in fluid and electrolyte disturbances.
Excessive use of the laxative effects of magnesium hydroxide may result in abdominal cramping, nausea and/or diarrhea.
In overdose, symptoms of gastrointestinal irritation and/or watery diarrhea may occur.
Magnesium hydroxide poisoning can result in hypermagnesemia which includes symptoms of: nausea, vomiting, flushing, thirst, hypotension, drowsiness, confusion, loss of tendon reflexes, muscle weakness, respiratory depression, cardiac arrhythmias, coma and cardiac arrest.
Not to be used in individuals with any form of kidney disease or renal failure, a magnesium restricted diet or with any sudden changes in bowel movement lasting over two weeks. Also not to be used in those individuals with abdominal pain, nausea, vomiting, symptoms of appendicitis or myocardial damage, heart block, fecal impaction, rectal fissures, intestinal obstruction or perforation or renal disease. Not to be used in women who are about to deliver as magnesium crosses the placenta and is excreted in small amounts in breast milk.
Using magnesium hydroxide with aluminum hydroxide can decrease the absorption rate of these drugs.
Magnesium hydroxide can react with digoxin, dicoumerol and cimetidine.
Use of ibuprofen with magnesium hydroxide can increase the absorption of the ibuprofen.
Use of magnesium hydroxide with penicallamine, bisphosphates, ketoconazole, quinolones or tetracycline can decrease the absorption of these drugs.
Enteric-coated tablets can be prematurely released when taken with magnesium hydroxide.
It is important to routinely monitor levels of serum magnesium and potassium in patients using magnesium hydroxide.
Serum magnesium levels are necessary to determine how much magnesium is being absorbed and how much is being excreted by the kidneys. Excessive diarrhea can occur from use of magnesium hydroxide and thus it is important to also monitor serum potassium levels to ensure hypokalemia does not occur.
Through the ingestion of 0.5-1.5 grams (in adults) the magnesium hydroxide will act by simple acid neutralization in the stomach. The hydroxide ions from the magnesium hydroxide suspension will combine with the acidic H+ ions of the hydrochloric acid made by the stomachs parietal cells. This neutralization reaction will result in the formation of magnesium chloride and water.
Through the ingestion of 2-5 grams (in adults) the magnesium hydroxide acts as a laxative in the colon. The majority of the suspension is not absorbed in the intestinal tract and will create an osmotic effect to draw water into the gut from surrounding tissues. With this increase of water in the intestines, the feces will soften and the intraluminal volume of the feces will increase. These effects still stimulate intestinal motility and induce the urge to defecate. Magnesium hydroxide will also release cholecystokinin (CCK) in the intestines which will accumulate water and electrolytes in the lumen and furthermore increase intestinal motility.
As a laxative, the magnesium hydroxide works by increasing the osmotic effect in the intestinal tract and drawing water in. This creates distension of the colon which results in an increase in peristaltic movement and bowel evacuation.
How the body processes this drug — absorption, distribution, metabolism, and elimination
ATC G04BX01
ATC A02AA04
Chemical identifiers
CAS, UNII, InChI Key and database cross-references
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Chemical identifiers
CAS, UNII, InChI Key and database cross-references
Linked compound data from DrugBank Open Data (CC BY-NC 4.0)
Magnesium hydroxide
DrugBank citations
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Structured knowledge from the free knowledge base
Molecular structure
Linked open data from Wikidata (Q407548), a free and open knowledge base operated by the Wikimedia Foundation. Data is available under the Creative Commons CC0 1.0 Public Domain Dedication. Molecular structure images from Wikimedia Commons.