Not Scheduled (OTC)

Oral

Plain Magnesium Hydroxide:

• Oral suspension: 400 mg/5 mL (commonly known as "Milk of Magnesia")

• Chewable tablets: 200 mg, 311 mg, 400 mg

Fixed-Dose Combinations (commonly available):

• Magnesium hydroxide + Aluminium hydroxide (suspension/tablets)

• Magnesium hydroxide + Aluminium hydroxide + Simethicone (suspension/tablets)

• Magnesium hydroxide + Aluminium hydroxide + Oxetacaine (suspension)

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Dyspepsia / Hyperacidity / Gastroesophageal Reflux (Symptomatic Relief)

Oral Suspension (400 mg/5 mL):

Parameter Dosing Details

Starting dose 5–10 mL orally as needed

Titration Not applicable (PRN use)

Usual maintenance dose 5–15 mL after meals and/or at bedtime

Maximum dose 60 mL/day (divided into up to 4 doses)

Chewable Tablets:

Parameter Dosing Details

Starting dose 200–400 mg (1–2 tablets) chewed thoroughly, as needed

Titration Not applicable

Usual maintenance dose 400–800 mg after meals and at bedtime

Maximum dose 2400 mg/day (divided into up to 4 doses)

Key Clinical Notes:

• Administer 1–3 hours after meals and at bedtime for optimal acid neutralization

• Chew tablets completely before swallowing; follow with water

• Short-term symptomatic use only; if symptoms persist >2 weeks, investigate underlying cause

• Combination with aluminium hydroxide reduces diarrhoea risk (magnesium laxative effect balanced by aluminium constipating effect)

1. Occasional Constipation (Short-term Relief)

Oral Suspension (Osmotic/Saline Laxative Action):

Parameter Dosing Details

Starting dose 15–30 mL orally as single dose

Titration Not applicable

Usual maintenance dose 15–30 mL once daily, preferably at bedtime

Maximum dose 60 mL/day

Key Clinical Notes:

• Onset of action: 30 minutes to 6 hours

• Works by osmotic water retention in intestinal lumen

• Ensure adequate fluid intake (at least 240 mL water with each dose)

• NOT for regular or chronic use (risk of electrolyte imbalance, dependency)

• Limit use to 3–7 days maximum

Secondary Indications — Adults Only (Off-label)

Indication Dose Duration Notes

Magnesium supplementation (mild hypomagnesaemia) (OFF-LABEL) 400–800 mg orally twice daily Until magnesium levels normalize Specialist supervision. Oral magnesium hydroxide has variable absorption; magnesium oxide or citrate may be preferred. Monitor serum magnesium.

Note: Magnesium hydroxide is NOT indicated for eclampsia/pre-eclampsia (magnesium sulfate IV is the standard treatment).

PAEDIATRIC DOSING (Specialist Only)

Primary Indications

1. Occasional Constipation (Short-term Relief)

⚠️ NOT recommended below 2 years of age

Oral Suspension (400 mg/5 mL):

2–5 years 2.5 mL once daily 2.5–5 mL once daily 5 mL/day

6–11 years 5 mL once daily 5–15 mL once daily 15 mL/day

≥12 years 15 mL once daily 15–30 mL once daily 30–45 mL/day

Key Clinical Notes:

• Administer at bedtime with adequate water

• Limit use to ≤3 days; address underlying cause if constipation persists

• Ensure adequate hydration

• PEG (polyethylene glycol) or lactulose preferred for chronic constipation in children

1. Dyspepsia / Hyperacidity (Occasional Symptomatic Use)

6–11 years 5–10 mL suspension After meals/at bedtime as needed Short-term only; max 2 weeks

≥12 years Adult dosing — —

Secondary Indications — Paediatric (Off-label)

Not applicable — no established off-label paediatric indications in Indian practice.

Clear Statement: NOT recommended below 2 years of age except under paediatric gastroenterologist supervision. Use in children 2–6 years should be limited to short-term with adequate hydration monitoring.

Safety Monitoring in Children:

• Monitor hydration status and stool output

• Watch for signs of diarrhoea-induced dehydration

• Avoid prolonged use

Mild impairment (eGFR 60–89) Use with caution; limit to short-term occasional use

Moderate impairment (eGFR 30–59) Avoid regular use; if essential, use lowest dose and monitor serum magnesium

Severe impairment (eGFR <30) AVOID — significant risk of hypermagnesaemia due to impaired renal magnesium excretion

Dialysis patients AVOID — hypermagnesaemia risk; magnesium-free alternatives preferred

Note: Even occasional use in moderate-severe renal impairment can cause magnesium accumulation. Hypermagnesaemia manifests as lethargy, hypotension, respiratory depression, and cardiac conduction abnormalities.

• Known hypersensitivity to magnesium compounds

• Severe renal impairment or renal failure (eGFR <30 mL/min/1.73m²)

• Gastrointestinal obstruction (complete or partial)

• Paralytic ileus

• Appendicitis or undiagnosed acute abdominal pain

• Acute surgical abdomen

• Faecal impaction (may worsen with saline laxative)

• Rectal bleeding of unknown cause

• Myasthenia gravis (magnesium may worsen neuromuscular weakness)

• Elderly patients — increased sensitivity to electrolyte disturbances; reduced renal reserve

• Mild-moderate renal impairment — risk of magnesium accumulation with repeated use

• Cardiac conduction abnormalities — hypermagnesaemia can worsen heart block

• Patients on low-sodium diet — some suspensions contain sodium

• Chronic use — risk of electrolyte imbalance, laxative dependency, acid-base disturbance

• Concurrent diuretic use — may alter magnesium/electrolyte balance

• Patients with inflammatory bowel disease — use cautiously

• Dehydration risk — ensure adequate fluid intake when used as laxative

• Enteric-coated medications — alkaline environment may cause premature tablet dissolution

Parameter Details

Risk Category Generally considered safe for occasional short-term use; minimal systemic absorption

Preferred alternatives First-line for constipation: Dietary modification, bulk-forming laxatives (ispaghula), lactulose. First-line for heartburn: Lifestyle modification, sucralfate, calcium carbonate antacids.

When may be used Occasional use for constipation or dyspepsia when other measures insufficient; avoid regular use

Monitoring Monitor for excessive diarrhoea, dehydration, electrolyte disturbance with frequent use

Note: Excessive doses may cause diarrhoea leading to fluid/electrolyte loss; avoid prolonged use.

Parameter Details

Compatibility Compatible with breastfeeding

Preferred alternatives Calcium carbonate for dyspepsia; lactulose/PEG for constipation (if chronic use needed)

Drug levels in milk Low — minimal systemic absorption; magnesium naturally present in breast milk

Infant monitoring Monitor for loose stools in breastfed infant if mother taking high/frequent doses

Parameter Recommendation

Starting dose Use lowest effective dose (e.g., 5 mL suspension for antacid; 15 mL for laxative)

Titration Not applicable; PRN use only

Special risks Increased sensitivity to magnesium-induced diarrhoea; dehydration risk; electrolyte imbalance; reduced renal reserve (even if serum creatinine appears normal); higher risk of hypermagnesaemia with repeated dosing

Monitoring Assess renal function before regular use; monitor hydration status

Recommendation Avoid chronic use; prefer alternatives (PEG, lactulose) for regular constipation management

Interacting Drug Mechanism & Effect Management

Tetracyclines (doxycycline, tetracycline) Chelation reduces antibiotic absorption by up to 90% Separate by at least 2–3 hours (ideally tetracycline 1 hour before or 2 hours after antacid)

Fluoroquinolones (ciprofloxacin, levofloxacin, ofloxacin) Chelation significantly reduces quinolone absorption Separate by at least 2–4 hours (quinolone 2 hours before or 4–6 hours after antacid)

Bisphosphonates (alendronate, risedronate) Chelation reduces bisphosphonate absorption Separate by at least 2 hours; take bisphosphonate on empty stomach with plain water only

Iron supplements (ferrous sulfate, ferrous fumarate) Chelation reduces iron absorption Separate by at least 2–4 hours

Mycophenolate mofetil Reduced absorption of mycophenolate Avoid concurrent use or separate by at least 2 hours

Interacting Drug Effect Management

Levothyroxine Reduced absorption; may impair thyroid control Separate by at least 4 hours

Digoxin Reduced absorption; diarrhoea may further reduce bioavailability Separate administration; monitor digoxin levels if symptomatic

Ketoconazole / Itraconazole Reduced absorption (require acidic environment for dissolution) Separate by at least 2 hours; consider alternative antifungal

Gabapentin / Pregabalin May reduce absorption Separate by at least 2 hours

Penicillamine Reduced absorption Separate by at least 2 hours

Other antacids / Laxatives Additive effects; increased diarrhoea risk Avoid combining multiple magnesium-containing products

Quinidine Magnesium may enhance effects; alkaline urine reduces quinidine excretion Monitor for quinidine toxicity

Sodium polystyrene sulfonate (Kayexalate) Intestinal alkalinisation may reduce efficacy Avoid concurrent use

• Diarrhoea (dose-limiting; most common)

• Abdominal cramping/discomfort

• Flatulence

• Nausea

• Chalky/unpleasant taste

Adverse Effect Clinical Notes

Hypermagnesaemia (in renal impairment) Presents with lethargy, confusion, hypotension, bradycardia, respiratory depression, muscle weakness, areflexia. Severe cases: cardiac arrest. Requires immediate discontinuation and IV calcium gluconate.

Severe dehydration Secondary to excessive diarrhoea; especially in elderly and children

Electrolyte disturbances Hyponatraemia, hypokalaemia with chronic use; requires monitoring

Metabolic alkalosis With prolonged high-dose use

Bowel obstruction worsening If used in undiagnosed abdominal pain with underlying obstruction

Aspiration Risk if given to obtunded patient

During short-term use Monitor stool frequency; assess for excessive diarrhoea and dehydration

If used regularly (not recommended) Serum magnesium, electrolytes (sodium, potassium), renal function every 2–4 weeks initially

Long-term NOT recommended for chronic use; if unavoidable, monitor magnesium and electrolytes monthly

Plain Magnesium Hydroxide:

• Milk of Magnesia® (Abbott/Parke-Davis)

• MOM® (various generics)

• Cremaffin® (plain — Abbott)

Fixed-Dose Combinations (Mg hydroxide + Al hydroxide ± Simethicone):

• Digene® (Abbott) — tablets, gel, suspension

• Gelusil® (Pfizer) — tablets, suspension

• Gelusil MPS® (with simethicone)

• Maalox® (Sanofi)

• Polycrol® (Indoco)

Fixed-Dose Combinations (with Oxetacaine):

• Mucaine® (Abbott) — gel, suspension

• Tricaine MPS® (various)

Note: Magnesium hydroxide is NOT listed in NLEM 2022. Not under NPPA price control. Widely available OTC.

1. Combination antacids balance effects — magnesium hydroxide causes diarrhoea while aluminium hydroxide causes constipation; combination products (Digene, Gelusil) provide balanced effect with reduced GI side effects.

1. Timing of drug interactions critical — magnesium hydroxide chelates multiple drugs. Counsel patients to separate from antibiotics (fluoroquinolones, tetracyclines), thyroid medications, and bisphosphonates by at least 2–4 hours.

1. Avoid in renal impairment — even moderate renal dysfunction increases hypermagnesaemia risk with repeated dosing. Calcium-based antacids or aluminium hydroxide preferred in CKD patients.

1. Not for chronic constipation — saline laxatives like magnesium hydroxide are for occasional short-term use only. For chronic constipation, prefer osmotic laxatives (PEG, lactulose) or bulk-forming agents.

1. Elderly require caution — reduced renal reserve (even with "normal" creatinine) increases toxicity risk. Start with lowest effective dose; avoid regular use.

1. Not a magnesium supplement — despite magnesium content, oral hydroxide has variable absorption and is not reliable for treating hypomagnesaemia. Use magnesium oxide, citrate, or IV magnesium sulfate for supplementation.

antacid; saline-laxative; constipation; hyperacidity; dyspepsia; OTC; renal-avoid; drug-interactions; magnesium-toxicity; elderly-caution; Magnesium Hydroxide

RxIndia v1.0 — 06 Jun 2025

• CDSCO Drug Database

• Indian Pharmacopoeia 2022

• API Textbook of Medicine (11th Edition)

• AIIMS Adult and Paediatric Formulary

• IAP Guidelines for Paediatric Constipation

• Goodman & Gilman's The Pharmacological Basis of Therapeutics (14th Edition)

• WHO Model List of Essential Medicines (supportive — paediatric section)

• Product package inserts (Milk of Magnesia®, Digene®, Mucaine®)