Adult: For the relief of heartburn, indigestion or upset stomach: As 400 mg/5 mL suspension: 5-15 mL up to 4 times daily, or as directed. As 2,400 mg/10 mL suspension: 5 mL. Max: 20 mL in 24 hours. Doses may be taken with water. As 1,325 mg/5 mL paste concentrated suspension: 5-10 mL diluted in small amount of water, as necessary. Dosage recommendations may vary among countries and individual products (refer to specific product guideline). Child: ≥12 years Same as adult dose.
Oral Constipation
Adult: For relief of occasional cases: As 400 mg/5 mL or 1,200 mg/15 mL suspension: 30-60 mL. As 2,400 mg/10 mL: 15-30 mL. All doses may be taken once daily (preferably at bedtime) or in divided doses, or as directed. As 800 mg/5 mL suspension: 10-20 mL once daily (preferably at bedtime). Drink a full glass of water with each dose. As 1,325 mg/5 mL paste concentrated suspension: 25-50 mL diluted in a glass of water to be taken at bedtime. Dosage recommendations may vary among countries and individual products (refer to specific product guideline). Child: For relief of occasional cases: 2-<6 years As 400 mg/5 mL or 1,200 mg/15 mL suspension; 400 mg chewable tablet: 400-1,200 mg daily as single or in divided doses (Max: 1,200 mg/day). As 800 mg/5 mL suspension: 800 mg once daily (preferably at bedtime) or as directed. 6-<12 years As 400 mg/5 mL or 1,200 mg/15 mL suspension; 400 mg chewable tablet: 1,200-2,400 mg daily as single or in divided doses (Max: 2,400 mg/day). As 800 mg/5 mL suspension: 800-1,600 mg once daily (preferably at bedtime). Drink a full glass of water with each dose. ≥12 years Same as adult dose. Dosage recommendations may vary among countries and individual products (refer to specific product guideline).
Renal Impairment
Severe renal failure: Contraindicated.
Contraindications
Acute gastrointestinal conditions; severe renal failure.
Special Precautions
Patients with myasthenia gravis or neuromuscular disease, sudden change in bowel habits (which persists for >2 weeks), Mg-restricted diet; stomach pain, nausea or vomiting. Debilitated patients. Renal and hepatic impairment. Children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Rarely, hypermagnesaemia (particularly in patients with renal impairment). Gastrointestinal disorders: Abdominal pain, diarrhoea (dose-dependent), colic.
Overdosage
Symptoms: Watery diarrhoea, gastrointestinal irritation; rarely, hypermagnesaemia which includes symptoms such as nausea, vomiting, thirst, flushing, drowsiness, hypotension, confusion, loss of tendon reflexes, muscle weakness, respiratory depression, cardiac arrhythmias, cardiac arrest and coma. Management: Administer Ca gluconate 10% 10-20 mL via IV to counteract respiratory depression or heart block. May give adequate fluids to patients with normal renal function to aid removal of Mg in the body. May perform haemodialysis in patients with renal impairment or severe hypermagnesaemia.
Drug Interactions
May decrease absorption of certain antibiotics (e.g. cefpodoxime, tetracyclines, quinolones), antifungals (e.g. itraconazole), antivirals (e.g. atazanavir, rilpivirine), fexofenadine, bisphosphonates (e.g. alendronic acid, ibandronic acid), corticosteroids (e.g. dexamethasone, deflazacort), antiepileptics (e.g. gabapentin, phenytoin), certain antipsychotics (e.g. sulpiride, chlorpromazine), ACE inhibitors (e.g. captopril), rosuvastatin, chloroquine, hydroxychloroquine, proguanil, digoxin, dipyridamole, levothyroxine, mycophenolate, iron preparations, nilotinib, and penicillamine. May increase absorption of ibuprofen. May decrease the excretion of quinidine. May enhance the adverse or toxic effect, particularly metabolic alkalosis, of sodium polystyrene sulfonate. Excretion of salicylates may be increased.
Action
Description: Magnesium hydroxide stimulates bowel movement by retaining fluid in the intestinal lumen which distends the colon, thus increasing peristalsis. It also neutralises stomach acid by reacting with hydrochloric acid in the stomach to form Mg chloride. Onset: Bowel movement: 30 minutes to 6 hours. Pharmacokinetics: Absorption: Mg: Poorly absorbed from the small intestine (approx 30%). Distribution: Mg: Crosses the placenta; enters breast milk (small amounts). Excretion: Mainly via urine (up to 30% as absorbed Mg ions); faeces (as unabsorbed drug).
Chemical Structure
Magnesium hydroxide Source: National Center for Biotechnology Information. PubChem Database. Milk of magnesia, CID=73981, https://pubchem.ncbi.nlm.nih.gov/compound/Milk-of-magnesia (accessed on Jan. 20, 2020)
A02AA04 - magnesium hydroxide ; Belongs to the class of magnesium-containing antacids.
References
Anon. Magnesium Hydroxide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/06/2021.Basic Care Milk of Magnesia (L. Perrigo Company). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/06/2021.Buckingham R (ed). Magnesium Hydroxide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/06/2021.CVS Health Children’s Saline Laxative Chewable Tablet (CVS Pharmacy, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.Dulcolax Liquid (Chattem, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.HOE’s Milk of Magnesia Oral Suspension (HOE Pharmaceuticals Sdn Bhd). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 24/08/2021.Humco Milk of Magnesia Suspension (Humco Holding Group, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.Joint Formulary Committee. Magnesium Hydroxide. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/06/2021.Magnesium Hydroxide Mixture 8% w/w Oral Suspension (Ayrton Saunders Ltd). MHRA. https://products.mhra.gov.uk. Accessed 10/06/2021.Magnesium Hydroxide Mixture BP (Thornton & Ross Ltd). MHRA. https://products.mhra.gov.uk. Accessed 10/06/2021.Milk of Magnesia Liquid (Aurohealth LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.Milk of Magnesia Suspension (Cardinal Health). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.Milk of Magnesia Suspension (Pharmaceutical Associates, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 24/08/2021.Pedia-Lax (C.B. Fleet Company, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/06/2021.Phillips’ Milk of Magnesia (Omega Pharma Ltd.). MHRA. https://products.mhra.gov.uk. Accessed 10/06/2021.
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