Usage
- Medical Conditions: Magnesium hydroxide is prescribed for the relief of occasional constipation, indigestion (dyspepsia), heartburn, and upset stomach caused by excess gastric acid. It is also used to prepare the bowels for certain medical procedures.
- Pharmacological Classification: Saline laxative, antacid.
- Mechanism of Action: As an antacid, magnesium hydroxide neutralizes stomach acid. As a laxative, it increases water content in the intestines, stimulating bowel movements.
Alternate Names
- Milk of Magnesia
- Brand names: Phillips’ Milk of Magnesia, Magnesia San Pellegrino
How It Works
- Pharmacodynamics: Neutralizes gastric acid by reacting with hydrochloric acid (HCl) in the stomach to form magnesium chloride (MgCl2) and water. Increases osmotic pressure within the intestinal lumen, drawing water into the gut and increasing stool volume. This stimulates peristalsis, promoting bowel evacuation.
- Pharmacokinetics: Poorly absorbed from the gastrointestinal tract. The small amount that is absorbed is excreted renally. Unabsorbed magnesium is eliminated in the feces.
- Mode of Action: Direct chemical neutralization of gastric acid (antacid effect); osmotic action in the intestine (laxative effect).
- Receptor Binding, Enzyme Inhibition, Neurotransmitter Modulation: Does not involve receptor binding, enzyme inhibition, or neurotransmitter modulation.
- Elimination Pathways: Primarily fecal excretion of unabsorbed magnesium; renal excretion of the small amount of absorbed magnesium.
Dosage
Standard Dosage
Adults:
- Antacid: 400-1200 mg orally as needed, up to four times a day.
- Laxative: 2400-4800 mg orally per day, preferably at bedtime.
- Maximum daily dose (as magnesium hydroxide): up to 7200 mg depending upon the formulation.
Children:
- Constipation:
- 2 to under 6 years: 400-1200 mg orally once a day or in divided doses. Maximum dose: 1200 mg/day.
- 6 to under 12 years: 1200-2400 mg orally once a day or in divided doses. Maximum dose: 2400 mg/day.
- Dyspepsia: Generally not recommended for children under 12.
- Consult a healthcare professional for specific pediatric dosing guidelines based on age and weight.
Special Cases:
- Elderly Patients: Use with caution due to potential for decreased renal function. Monitor for hypermagnesemia.
- Patients with Renal Impairment: Contraindicated in severe renal failure. Reduce dosage in moderate renal impairment and monitor serum magnesium levels.
- Patients with Hepatic Dysfunction: Generally no dose adjustment is needed, but use cautiously.
- Patients with Comorbid Conditions: Use with caution in patients with heart failure, edema, electrolyte imbalances.
Clinical Use Cases
- Intubation, Surgical Procedures, Mechanical Ventilation, ICU Use, Emergency Situations: Dosage will depend on the specific clinical context and should be determined by the healthcare professional. MgSO4 (Magnesium Sulphate) not Mg(OH)2 might be used in these settings.
Dosage Adjustments
- Adjust dosage based on renal function, patient response, and the presence of other medical conditions.
Side Effects
Common Side Effects
- Diarrhea
- Abdominal cramping
Rare but Serious Side Effects
- Hypermagnesemia (especially in patients with renal impairment) - symptoms may include nausea, vomiting, weakness, hypotension, and respiratory depression.
- Allergic reactions
Long-Term Effects
- Chronic use can lead to electrolyte imbalances.
Adverse Drug Reactions (ADR)
- Severe hypermagnesemia leading to cardiac or respiratory arrest.
Contraindications
- Severe renal impairment/failure
- Hypersensitivity to magnesium hydroxide
- Acute gastrointestinal conditions (e.g., appendicitis, bowel obstruction)
Drug Interactions
- Reduced absorption of tetracyclines, quinolones, iron supplements, bisphosphonates, and other medications.
- Consult a comprehensive drug interaction database for specific interactions.
Pregnancy and Breastfeeding
- Consult a physician before use during pregnancy and breastfeeding. Generally considered safe for occasional use, but prolonged use should be avoided.
Drug Profile Summary
- Mechanism of Action: Antacid (neutralizes gastric acid); Laxative (osmotic action).
- Side Effects: Diarrhea, abdominal cramping, hypermagnesemia (rare).
- Contraindications: Severe renal impairment, hypersensitivity, acute gastrointestinal conditions.
- Drug Interactions: Reduced absorption of certain medications (e.g., tetracyclines, quinolones).
- Pregnancy & Breastfeeding: Consult physician before use.
- Dosage: Varies depending on indication and patient factors (see dosage section).
- Monitoring Parameters: Serum magnesium levels (in patients with renal impairment).
Popular Combinations
- Simethicone (to reduce gas and bloating)
- Aluminum hydroxide (to reduce the risk of diarrhea)
Precautions
- General Precautions: Assess renal function, especially in elderly patients. Avoid prolonged use.
- Specific Populations (Pregnant Women, Breastfeeding Mothers, Children & Elderly): Consult a healthcare professional before use.
- Lifestyle Considerations: None specifically related to magnesium hydroxide.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Magnesium Hydroxide?
A: See dosage section for details based on age, condition, and formulation.
Q2: How quickly does Magnesium Hydroxide work for constipation?
A: Onset of action is typically within 30 minutes to 6 hours when used as a laxative.
Q3: Can I take Magnesium Hydroxide with other medications?
A: It can interact with certain medications, reducing their absorption. Separate doses by at least 2-3 hours. Consult a physician or pharmacist.
Q4: What are the signs of hypermagnesemia?
A: Nausea, vomiting, muscle weakness, hypotension, respiratory depression.
Q5: Is Magnesium Hydroxide safe for long-term use?
A: Prolonged use can lead to electrolyte imbalances and should generally be avoided.
Q6: What should I do if I miss a dose?
A: If used as needed for antacid effect, take as soon as remembered. If used as a laxative, skip the missed dose and take the next dose at the usual time.
Q7: Can Magnesium Hydroxide be used during pregnancy?
A: Consult with a physician before use during pregnancy.
Q8: Are there any dietary restrictions when taking Magnesium Hydroxide?
A: No specific dietary restrictions, but ensure adequate fluid intake, especially when used as a laxative.
Q9: Can I use Magnesium Hydroxide for children?
A: It can be used for children, but the dosage should be adjusted based on age and weight. Consult a pediatrician.
Q10: What should I do if I experience side effects?
A: Discontinue use and consult with a healthcare professional.
