Magnesium Hydroxide

For Constipation (Laxative)

• Standard Dose: 30 mL to 60 mL of standard-strength liquid (400 mg/5 mL) taken once daily, or in divided doses.
• Chewable Tablets: 8 to 16 tablets (311 mg each) per day.

For Indigestion (Antacid)

• Standard Dose: 5 mL to 15 mL of liquid up to four times daily as needed, or 2 to 4 chewable tablets as symptoms occur.

• Children 6 to 11 years: 15 mL to 30 mL of liquid daily for constipation.
• Children 2 to 5 years: 5 mL to 15 mL of liquid daily for constipation.
• Children under 2 years: Not recommended unless directed by a pediatrician.

Renal Impairment

Patients with significant kidney disease should avoid Magnesium Hydroxide. Reduced renal clearance can lead to toxic accumulation of magnesium (hypermagnesemia).

Hepatic Impairment

No specific dosage adjustments are typically required for liver disease, as the drug is not metabolized by the liver.

Elderly Patients

Older adults should start at the lower end of the dosing range due to the increased prevalence of decreased renal function.

• Administration: Shake the liquid suspension well before each use. Drink a full glass (8 oz) of water or other liquid with each dose to help the laxative effect and prevent dehydration.
• Timing: For constipation, it is often taken at bedtime to produce a bowel movement the next morning (usually within 30 minutes to 6 hours).
• Storage: Store at room temperature (68°F to 77°F). Do not freeze.

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not double the dose to catch up.

Signs of magnesium overdose include severe nausea, vomiting, muscle weakness, low blood pressure (hypotension), and irregular heartbeat. In severe cases, it can lead to respiratory distress or cardiac arrest. Seek emergency medical attention or contact a Poison Control Center immediately.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance.

• Diarrhea: Excessive doses or sensitivity can lead to very loose or watery stools.
• Abdominal Cramping: A sensation of tightening or discomfort in the stomach area as the intestines are stimulated.
• Nausea: A feeling of stomach upset, often occurring if the medication is taken on an empty stomach.

• Dehydration: Increased thirst or dry mouth due to the osmotic movement of water into the gut.
• Electrolyte Imbalance: Mild changes in blood levels of sodium, potassium, or calcium.

• Hypermagnesemia: Excessively high magnesium levels, primarily seen in those with undiagnosed kidney issues.
• Severe Allergic Reaction: Hives, difficulty breathing, or swelling of the face and throat.

> Warning: Stop taking Magnesium Hydroxide and call your doctor immediately if you experience any of these.

• Rectal Bleeding: This may indicate a more serious underlying condition or injury to the intestinal lining.
• No Bowel Movement: Failure to have a bowel movement after use may indicate a bowel obstruction.
• Severe Dizziness or Fainting: May be a sign of low blood pressure or significant electrolyte loss.
• Slow Heartbeat: A clinical sign of magnesium toxicity affecting the cardiac conduction system.
• Mental Confusion: Lethargy or altered mental status associated with high magnesium levels.

Prolonged use (more than 7 consecutive days) can lead to laxative dependence, where the bowels require the drug to function normally. Chronic use may also lead to persistent electrolyte imbalances and nutrient malabsorption.

No FDA black box warnings are currently issued for Magnesium Hydroxide. However, it carries significant warnings regarding use in patients with kidney disease.

Report any unusual symptoms to your healthcare provider.

Magnesium Hydroxide is intended for short-term use only. If symptoms persist for more than 7 days, you must consult a healthcare professional to rule out serious underlying conditions such as inflammatory bowel disease or colorectal cancer.

No FDA black box warnings for Magnesium Hydroxide.

• Allergic Reactions: Though rare, anaphylaxis can occur. Patients with a known hypersensitivity to magnesium salts should avoid this product.
• Renal Toxicity: In patients with impaired kidney function, the body cannot effectively clear magnesium. This can lead to life-threatening hypermagnesemia (magnesium toxicity).
• Appendicitis Risk: Do not use if you have symptoms of appendicitis or an inflamed bowel, such as severe stomach pain, nausea, and vomiting.
• Neuromuscular Disorders: Patients with conditions like Myasthenia Gravis should use magnesium supplements with caution, as magnesium can affect neuromuscular transmission.

For patients using Magnesium Hydroxide frequently, healthcare providers may monitor:

• Serum Electrolytes: Specifically magnesium, potassium, and calcium levels.
• Renal Function: Serum creatinine and Glomerular Filtration Rate (GFR).

Magnesium Hydroxide typically does not interfere with the ability to drive or operate machinery. However, if you experience significant dizziness due to dehydration, avoid these activities.

Alcohol can exacerbate gastrointestinal irritation and dehydration. While there is no direct chemical interaction, limiting alcohol is advised when treating digestive issues.

Magnesium Hydroxide can be stopped abruptly without a tapering schedule if used for short-term relief. If used chronically, consult a doctor to transition to high-fiber diets or other lifestyle modifications to prevent rebound constipation.

> Important: Discuss all your medical conditions with your healthcare provider before starting Magnesium Hydroxide.

There are no absolute drug-drug contraindications where use is strictly forbidden, but several combinations require extreme caution or timing adjustments.

• Neuromuscular Blockers: Magnesium can enhance the effects of medications like vecuronium or succinylcholine used during surgery, potentially leading to prolonged respiratory depression.
• Polystyrene Sulfonate: Use with this potassium-lowering medication can lead to metabolic alkalosis in patients with renal failure.

• Antibiotics (Tetracyclines and Fluoroquinolones): Magnesium binds to these drugs (chelation) in the GI tract, significantly reducing their absorption. Take Magnesium Hydroxide at least 2 hours before or 6 hours after these antibiotics.
• Bisphosphonates: Magnesium can reduce the absorption of osteoporosis medications like Alendronate.
• Thyroid Hormones: Magnesium may interfere with the absorption of Levothyroxine.

• High-Fiber Foods: While generally good for constipation, very high fiber intake at the exact same time as an antacid dose may slightly alter absorption rates.
• Dairy: Excessive calcium intake combined with magnesium antacids can occasionally lead to milk-alkali syndrome, though this is rare with magnesium alone.

• Vitamin D: High doses of Vitamin D can increase magnesium absorption, potentially increasing the risk of high magnesium levels in susceptible individuals.
• Calcium Supplements: May compete for absorption in the intestinal tract.

Magnesium Hydroxide may interfere with certain lab tests:

• Serum Gastrin: May be altered due to changes in gastric pH.
• Systemic pH: Excessive use can lead to a slight increase in urinary pH, affecting the excretion of other drugs.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking.

• Severe Renal Failure: Patients with a GFR below 30 mL/min should not use Magnesium Hydroxide due to the high risk of fatal magnesium toxicity.
• Hypersensitivity: Known allergy to any component of the formulation.

• Abdominal Pain of Unknown Origin: Use could mask symptoms of a serious condition like a perforated bowel or appendicitis.
• Bowel Obstruction: Using a laxative when the bowel is physically blocked can lead to intestinal rupture.
• Electrolyte Imbalance: Patients already suffering from high magnesium or low calcium levels should use this with extreme caution.

There is no significant cross-sensitivity reported between Magnesium Hydroxide and other classes of laxatives (like stimulants or stool softeners), though patients sensitive to other magnesium salts (magnesium citrate, magnesium sulfate) will likely react similarly to Magnesium Hydroxide.

> Important: Your healthcare provider will evaluate your complete medical history before prescribing Magnesium Hydroxide.

Magnesium Hydroxide is generally considered safe for short-term use during pregnancy when used at recommended OTC doses. It is often categorized as Category B. However, it should only be used if clearly needed and under the supervision of an obstetrician, as excessive use can lead to electrolyte disturbances in the mother.

Small amounts of magnesium are distributed into breast milk, but at standard doses, it is considered compatible with breastfeeding by the American Academy of Pediatrics. No adverse effects on nursing infants have been documented with maternal use of Magnesium Hydroxide.

Approved for children as young as 2 years old for constipation. It is not approved for infants under 2 years unless specifically directed by a physician. Long-term use in children is discouraged as it may interfere with normal bowel habit development.

Older adults are at a higher risk for dehydration and electrolyte imbalances. Because renal function naturally declines with age, the risk of magnesium accumulation is higher. Healthcare providers often recommend lower doses and monitoring of kidney function.

Magnesium Hydroxide is largely contraindicated in severe renal impairment. In mild-to-moderate impairment, it should only be used under strict medical supervision with frequent monitoring of serum magnesium levels.

No dosage adjustments are typically required for patients with liver disease, as the elimination of magnesium is not dependent on hepatic function.

> Important: Special populations require individualized medical assessment.

Magnesium Hydroxide is a basic compound that neutralizes gastric acid (HCl) to form magnesium chloride and water. This increases gastric pH, inhibiting the proteolytic action of pepsin. As a laxative, it exerts an osmotic effect, drawing water into the small and large intestines. This accumulation of fluid creates distention, which mechanically stimulates the stretch receptors in the enteric nervous system, triggering peristaltic movement.

• Onset of Action: Antacid effects are almost immediate (within minutes). Laxative effects typically occur within 30 minutes to 6 hours.
• Duration: The antacid effect lasts approximately 20-60 minutes on an empty stomach and up to 3 hours if taken after a meal.
• Tolerance: Physical tolerance to the osmotic effect is rare, but psychological dependence can occur.

| Parameter | Value |

|---|---|

| Bioavailability | 15-30% (as magnesium ion) |

| Protein Binding | 30% (to albumin) |

| Half-life | N/A (Excreted as ion) |

| Tmax | 0.5 - 6 hours (for laxative effect) |

| Metabolism | None (Inorganic salt) |

| Excretion | Renal (absorbed portion); Fecal (unabsorbed) |

• Molecular Formula: Mg(OH)2
• Molecular Weight: 58.32 g/mol
• Solubility: Practically insoluble in water and alcohol; soluble in dilute acids.
• Structure: A white, odorless powder that forms a suspension in water (Milk of Magnesia).

Magnesium Hydroxide is classified as a Saline Laxative and a Magnesium-containing Antacid. It is distinct from stimulant laxatives (like senna) and bulk-forming laxatives (like psyllium).