Magnesium Oxide 400mg Tablets
It is used to treat or prevent low magnesium levels.It is used to treat heartburn and upset stomach.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Mineral supplement, Laxative, Antacid
Pharmacologic Class
Electrolyte, Osmotic laxative, Antacid
Pregnancy Category
Category B
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Magnesium oxide is a mineral supplement that helps your body function properly. It can also be used to treat occasional constipation by drawing water into your intestines, or to relieve heartburn by neutralizing stomach acid.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with food and a full glass of water. It's essential to note that this medication may interfere with the absorption of other oral medications. If you take other medications by mouth, consult your doctor about the best time to take them in relation to this medication.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless instructed to do so. Instead, consult your pharmacist for guidance on the proper disposal method or inquire about potential drug take-back programs in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with food and a full glass of water. It's essential to note that this medication may interfere with the absorption of other oral medications. If you take other medications by mouth, consult your doctor about the best time to take them in relation to this medication.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless instructed to do so. Instead, consult your pharmacist for guidance on the proper disposal method or inquire about potential drug take-back programs in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Drink plenty of fluids (6-8 glasses of water daily) when using as a laxative.
- Maintain a balanced diet rich in fiber to support bowel regularity.
- Separate administration from other medications by at least 2-4 hours to avoid interactions.
Available Forms & Alternatives
Available Strengths:
- Magnesium Oxide 400mg Tablets
- Magnesium Sulfate 50% Inj, 10ml
- Magnesium 500mg Tablets
- Magnesium Sulfate 40mg/ml Inj, 50ml
- Magnesium Chloride 20% Inj, 50ml
- Magnesium Sulf 40mg/ml Inj, 100ml
- Magnesium Sulfate 50% Inj, 50ml
- Magnesium 200mg Tablets
- Magnesium Sulfate 50% Inj, 2ml
- Magnesium 300mg Capsules
- Magnesium Sulfate 40mg/ml Inj, 50ml
- Magnesium Sulfate 80mg/ml Inj, 50ml
- Magnesium 250mg Tablets
- Magnesium Sulfate 80mg/ml Inj
- Magn Sulf/d5w 10mg/ml Inj, 100ml
- Magnesium Oxide 250mg Tablets
- Magnesium Citrate Soln Lemon 296ml
- Magnesium Sulfate 50% Inj, 20ml
- Magnesium Su 40g/1000ml Inj, 1000ml
- Magnesium Sulfate 20gm/500ml Inj
Dosing & Administration
Adult Dosing
Standard Dose:
Varies by indication. For magnesium deficiency: 400-800 mg (1-2 tablets) daily. For laxative: 1.2-2.4 g (3-6 tablets) daily in divided doses or at bedtime. For antacid: 400-800 mg (1-2 tablets) as needed.
Dose Range:
400 - 2400 mg
Condition-Specific Dosing:
magnesiumDeficiency:
400-800 mg daily
constipation:
1.2-2.4 g daily in divided doses or at bedtime
dyspepsia/heartburn:
400-800 mg as needed
Pediatric Dosing
Neonatal:
Not established (use only under medical supervision)
Infant:
Not established (use only under medical supervision)
Child:
Not established for 400mg tablets; dosing for magnesium deficiency or constipation is weight-based and should be under medical supervision. Typically lower doses of other magnesium forms.
Adolescent:
For constipation: 400-800 mg once daily or as directed by physician. For deficiency: as directed by physician.
Dose Adjustments
Renal Impairment:
Mild:
Use with caution, monitor serum magnesium.
Moderate:
Reduce dose significantly or avoid due to risk of hypermagnesemia.
Severe:
Contraindicated due to high risk of hypermagnesemia.
Dialysis:
Contraindicated due to high risk of hypermagnesemia.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed.
Pharmacology
Mechanism of Action
As a mineral supplement, magnesium is an essential cofactor for over 300 enzymatic reactions, including ATP production, nucleic acid and protein synthesis, and muscle contraction. As a laxative, magnesium oxide acts as an osmotic agent, drawing water into the intestinal lumen, which softens stool and promotes bowel evacuation. As an antacid, it neutralizes gastric acid by reacting with hydrochloric acid in the stomach to form magnesium chloride and water.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 25-60% (variable depending on dose and individual factors)
Tmax:
Not well-defined for oral magnesium oxide; absorption is gradual.
FoodEffect:
Food may slightly enhance absorption or reduce gastrointestinal upset.
Distribution:
Vd:
Not typically reported for magnesium; widely distributed throughout the body.
ProteinBinding:
Approximately 30% bound to albumin.
CnssPenetration:
Limited under normal physiological conditions; high serum levels can lead to CNS depression.
Elimination:
HalfLife:
Plasma half-life is variable (2-4 hours), but overall body turnover is much longer.
Clearance:
Primarily renal excretion.
ExcretionRoute:
Renal (urine), small amounts in feces.
Unchanged:
100% (as an ion)
Pharmacodynamics
OnsetOfAction:
Laxative effect: 0.5-6 hours; Antacid effect: immediate; Supplement effect: gradual (days to weeks).
PeakEffect:
Laxative effect: 2-8 hours.
DurationOfAction:
Laxative effect: variable; Antacid effect: short (1-3 hours).
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention, as they may be signs of a severe and potentially life-threatening reaction:
- Allergic reaction symptoms, such as rash, hives, itching, redness, swelling, blistering, or peeling skin, with or without fever
- Respiratory issues, including wheezing, tightness in the chest or throat, trouble breathing, swallowing, or talking
- Unusual hoarseness
- Swelling of the mouth, face, lips, tongue, or throat
Other Possible Side Effects
Like all medications, this drug can cause side effects, although not everyone will experience them. Many people have either no side effects or only mild ones. If you encounter any of the following side effects or any other unusual effects that bother you or do not go away, contact your doctor:
- Diarrhea
Note: This list does not include all possible side effects. If you have concerns about side effects, consult your doctor. For medical advice about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention, as they may be signs of a severe and potentially life-threatening reaction:
- Allergic reaction symptoms, such as rash, hives, itching, redness, swelling, blistering, or peeling skin, with or without fever
- Respiratory issues, including wheezing, tightness in the chest or throat, trouble breathing, swallowing, or talking
- Unusual hoarseness
- Swelling of the mouth, face, lips, tongue, or throat
Other Possible Side Effects
Like all medications, this drug can cause side effects, although not everyone will experience them. Many people have either no side effects or only mild ones. If you encounter any of the following side effects or any other unusual effects that bother you or do not go away, contact your doctor:
- Diarrhea
Note: This list does not include all possible side effects. If you have concerns about side effects, consult your doctor. For medical advice about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe or persistent diarrhea
- Muscle weakness or feeling very tired
- Dizziness or lightheadedness
- Slow or irregular heartbeat
- Difficulty breathing
- Confusion or changes in mental status
- No bowel movement after 3 days of laxative use
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins.
* Any existing health problems, as this medication may interact with other drugs or health conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins.
* Any existing health problems, as this medication may interact with other drugs or health conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your other medications and health conditions. Always consult your doctor before starting, stopping, or changing the dose of any medication.
Precautions & Cautions
It is essential to inform all of your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Adhere to your doctor's prescribed treatment duration and do not exceed the recommended duration of use. If you are pregnant, planning to become pregnant, or are currently breast-feeding, notify your doctor promptly. You and your doctor will need to discuss the potential benefits and risks of this medication to both you and your baby to make an informed decision.
Overdose Information
Overdose Symptoms:
- Severe diarrhea
- Nausea
- Vomiting
- Profound muscle weakness
- Lethargy
- Drowsiness
- Confusion
- Low blood pressure (hypotension)
- Slow heart rate (bradycardia)
- Respiratory depression (slow, shallow breathing)
- Coma
- Cardiac arrest
What to Do:
Immediately call 911 or your local poison control center (1-800-222-1222 in the US). Treatment may involve intravenous calcium gluconate to counteract magnesium's effects, fluid administration, and in severe cases, dialysis to remove excess magnesium.
Drug Interactions
Contraindicated Interactions
- Severe renal impairment (CrCl < 30 mL/min)
Major Interactions
- Tetracyclines (e.g., doxycycline, minocycline): Reduced absorption of tetracycline.
- Fluoroquinolones (e.g., ciprofloxacin, levofloxacin): Reduced absorption of fluoroquinolone.
- Bisphosphonates (e.g., alendronate, risedronate): Reduced absorption of bisphosphonate.
- Thyroid hormones (e.g., levothyroxine): Reduced absorption of thyroid hormone.
Moderate Interactions
- Calcium channel blockers (e.g., amlodipine, nifedipine): Additive hypotensive effects, increased risk of CNS depression.
- Neuromuscular blockers (e.g., rocuronium, succinylcholine): Enhanced neuromuscular blockade.
- Potassium-sparing diuretics (e.g., spironolactone, amiloride): Increased risk of hyperkalemia if renal function is impaired.
- Digoxin: May alter absorption, monitor digoxin levels.
- Iron salts: Reduced absorption of iron.
Minor Interactions
- Cellulose sodium phosphate: May bind magnesium and reduce absorption.
Monitoring
Baseline Monitoring
Renal function (Serum Creatinine, eGFR/CrCl)
Rationale: Magnesium is primarily renally excreted; impairment increases hypermagnesemia risk.
Timing: Before initiating therapy, especially in elderly or those with known renal issues.
Serum Magnesium levels
Rationale: To establish baseline if treating deficiency or if patient is at high risk for electrolyte imbalance.
Timing: Before initiation for deficiency, or if renal impairment/high dose.
Routine Monitoring
Serum Magnesium levels
Frequency: Periodically (e.g., weekly to monthly) for long-term use, high doses, or in patients with renal impairment.
Target: 1.7-2.2 mg/dL (0.7-0.9 mmol/L)
Action Threshold: >2.5 mg/dL (1.03 mmol/L) warrants dose reduction/discontinuation; >4.0 mg/dL (1.65 mmol/L) is critical.
Bowel habits
Frequency: Daily (for laxative use)
Target: Regular, soft bowel movements
Action Threshold: Excessive diarrhea or no bowel movement after 3 days (for laxative use).
Signs/symptoms of hypermagnesemia
Frequency: Daily
Target: Absence of symptoms
Action Threshold: Muscle weakness, lethargy, confusion, nausea, vomiting, hypotension, bradycardia, respiratory depression.
Symptom Monitoring
- Diarrhea
- Abdominal cramping
- Nausea
- Vomiting
- Muscle weakness
- Lethargy
- Dizziness
- Confusion
- Slowed heart rate (bradycardia)
- Low blood pressure (hypotension)
- Difficulty breathing
Special Patient Groups
Pregnancy
Generally considered safe for short-term use at recommended doses for magnesium supplementation or occasional constipation. Magnesium is an essential nutrient during pregnancy. Consult a healthcare provider before use.
Trimester-Specific Risks:
First Trimester:
No known specific risks at therapeutic doses.
Second Trimester:
No known specific risks at therapeutic doses.
Third Trimester:
No known specific risks at therapeutic doses. High doses or prolonged use, especially close to delivery, should be avoided due to potential for neonatal hypermagnesemia.
Lactation
Likely compatible with breastfeeding. Magnesium is a normal component of breast milk and is essential for infant development. Therapeutic doses are unlikely to cause adverse effects in the infant.
Infant Risk:
Low risk. Monitor infant for signs of diarrhea if mother is taking high doses.
Pediatric Use
Use with caution, especially as a laxative, due to the increased risk of electrolyte imbalance and dehydration in children. Dosing should be weight-based and strictly under medical supervision. Not recommended for infants or young children without a doctor's advice.
Geriatric Use
Increased risk of hypermagnesemia due to age-related decline in renal function. Start with lower doses and monitor renal function and serum magnesium levels closely. More susceptible to adverse effects like diarrhea and dehydration.
Clinical Information
Clinical Pearls
- Magnesium oxide has lower bioavailability compared to other magnesium salts (e.g., citrate, gluconate) when used for supplementation, but its high elemental magnesium content makes it useful.
- Advise patients to take interacting medications (e.g., tetracyclines, fluoroquinolones, bisphosphonates, thyroid hormones) at least 2-4 hours before or after magnesium oxide to minimize absorption issues.
- Emphasize the importance of adequate fluid intake when using magnesium oxide as a laxative to prevent dehydration and enhance its osmotic effect.
- Educate patients on the signs and symptoms of hypermagnesemia, especially those with impaired renal function, and when to seek immediate medical attention.
- Magnesium oxide is not intended for long-term daily use as a laxative without medical supervision, as it can lead to dependence or electrolyte imbalances.
Alternative Therapies
- For magnesium deficiency: Magnesium gluconate, magnesium aspartate, magnesium L-threonate (for CNS penetration).
- For constipation: Fiber supplements (psyllium, methylcellulose), stool softeners (docusate), other osmotic laxatives (polyethylene glycol, lactulose), stimulant laxatives (senna, bisacodyl).
- For antacid: Calcium carbonate, aluminum hydroxide, H2-receptor antagonists (ranitidine, famotidine), proton pump inhibitors (omeprazole, pantoprazole).
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets
Generic Available:
Yes
Insurance Coverage:
Often available over-the-counter (OTC) and may not be covered by prescription insurance plans unless prescribed by a physician.
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it occurred.