Mag-Oxide 420mg 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
Magnesium Supplement; Antacid; Laxative
Pharmacologic Class
Mineral Supplement; Antacid (Neutralizing Agent); Osmotic Laxative
Pregnancy Category
Category B
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Magnesium oxide is a mineral supplement that can also be used as an antacid to relieve heartburn and indigestion, or as a laxative to treat occasional constipation. It works by neutralizing stomach acid, drawing water into the intestines to soften stool, and providing essential magnesium to the body.
How to Use This Medicine
Taking Your Medication Correctly
To ensure you get the most benefit from your medication, follow these steps:
Take your medication exactly as directed by your doctor.
Read all the information provided with your medication and follow the instructions carefully.
Take your 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, you may need to take them at a different time than your current medication. Consult with your doctor to determine the best schedule for your medications.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication:
Store it at room temperature in a dry place, avoiding bathrooms and areas prone to moisture.
Keep all medications in a secure location, out of the reach of children and pets.
Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist or healthcare provider. Check with your pharmacist for guidance on the best disposal methods, and consider participating in local drug take-back programs.
What to Do If You Miss a Dose
If you miss a dose, follow these steps:
Take the missed dose as soon as you remember.
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 ensure you get the most benefit from your medication, follow these steps:
Take your medication exactly as directed by your doctor.
Read all the information provided with your medication and follow the instructions carefully.
Take your 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, you may need to take them at a different time than your current medication. Consult with your doctor to determine the best schedule for your medications.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication:
Store it at room temperature in a dry place, avoiding bathrooms and areas prone to moisture.
Keep all medications in a secure location, out of the reach of children and pets.
Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist or healthcare provider. Check with your pharmacist for guidance on the best disposal methods, and consider participating in local drug take-back programs.
What to Do If You Miss a Dose
If you miss a dose, follow these steps:
Take the missed dose as soon as you remember.
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 (at least 6-8 glasses of water daily) when using as a laxative to prevent dehydration and aid its effect.
- Maintain a balanced diet rich in fiber to support regular bowel movements.
- Engage in regular physical activity to promote healthy digestion.
- Avoid taking other medications within 2-4 hours of magnesium oxide, especially antibiotics (tetracyclines, fluoroquinolones), thyroid hormones, and bisphosphonates, as magnesium can interfere with their absorption.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Varies by indication. For magnesium supplementation: 400-800 mg elemental magnesium daily (Mag-Oxide 420mg contains 252mg elemental Mg). For constipation: 840-1680 mg (2-4 tablets) at bedtime. For antacid: 420-840 mg (1-2 tablets) as needed.
Dose Range:
420 - 1680 mg
Condition-Specific Dosing:
Magnesium Deficiency:
420-840 mg (1-2 tablets) once or twice daily, adjusted based on serum magnesium levels and clinical response.
Constipation (Laxative):
840-1680 mg (2-4 tablets) once daily at bedtime, or in divided doses.
Indigestion/Heartburn (Antacid):
420-840 mg (1-2 tablets) as needed, up to 4 times daily.
Pediatric Dosing
Neonatal:
Not established (use with extreme caution, only under medical supervision for specific conditions like hypomagnesemia).
Infant:
Not established (use with extreme caution, only under medical supervision for specific conditions like hypomagnesemia).
Child:
Not generally recommended as a laxative for children under 6 years without medical advice. For magnesium supplementation, dosing is weight-based and should be determined by a physician. Typical doses for constipation (6-11 years): 420-840 mg (1-2 tablets) once daily.
Adolescent:
For magnesium supplementation: 420-840 mg (1-2 tablets) once or twice daily. For constipation: 840-1680 mg (2-4 tablets) once daily.
Dose Adjustments
Renal Impairment:
Mild:
Use with caution; monitor serum magnesium levels.
Moderate:
Significant dose reduction required; monitor serum magnesium levels closely. 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 an antacid, magnesium oxide neutralizes gastric acid by reacting with hydrochloric acid in the stomach to form magnesium chloride and water. As a laxative, it acts as an osmotic agent, drawing water into the intestinal lumen, which increases stool volume and stimulates peristalsis. As a magnesium supplement, it provides elemental magnesium, an essential cation involved in numerous physiological processes including enzyme activity, nerve and muscle function, and bone formation.
Pharmacokinetics
Absorption:
Bioavailability:
Variable (approximately 15-30% of elemental magnesium is absorbed from the GI tract, depending on dose and magnesium status).
Tmax:
Not readily applicable for antacid/laxative effect. For systemic absorption, peak serum levels are reached within 2-6 hours.
FoodEffect:
Food may slightly decrease absorption rate but not extent.
Distribution:
Vd:
Not readily quantifiable for magnesium; widely distributed throughout the body. Approximately 50-60% is found in bone, 20-30% in muscle, and the remainder in soft tissues and extracellular fluid.
ProteinBinding:
Approximately 30% of serum magnesium is protein-bound (primarily to albumin).
CnssPenetration:
Limited under normal conditions; can cross the blood-brain barrier, especially at high concentrations.
Elimination:
HalfLife:
Not a typical pharmacokinetic parameter for an ion; serum half-life is approximately 20-24 hours for absorbed magnesium.
Clearance:
Primarily renal clearance.
ExcretionRoute:
Unabsorbed magnesium is excreted in feces. Absorbed magnesium is primarily excreted by the kidneys.
Unchanged:
100% (as magnesium ion)
Pharmacodynamics
OnsetOfAction:
Antacid: Rapid (within minutes). Laxative: 0.5 to 6 hours. Supplementation: Days to weeks for clinical effect.
PeakEffect:
Antacid: Within 30 minutes. Laxative: 2-8 hours.
DurationOfAction:
Antacid: 1-3 hours. Laxative: Varies, typically results in a single bowel movement.
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ 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 many people may not experience any side effects or only minor ones, it's essential to monitor your body's response. If you experience any of the following side effects or any other unusual symptoms that bother you or persist, contact your doctor for guidance:
Diarrhea
Important Note
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, don't hesitate to reach out to your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor is available to provide medical advice about side effects, so don't hesitate to contact them.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ 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 many people may not experience any side effects or only minor ones, it's essential to monitor your body's response. If you experience any of the following side effects or any other unusual symptoms that bother you or persist, contact your doctor for guidance:
Diarrhea
Important Note
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, don't hesitate to reach out to your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor is available to provide medical advice about side effects, so don't hesitate to contact them.
Seek Immediate Medical Attention If You Experience:
- Severe diarrhea or watery stools
- Abdominal pain or cramping that worsens
- Nausea or vomiting that doesn't go away
- Unusual tiredness or weakness
- Dizziness or lightheadedness
- Slow heartbeat
- Difficulty breathing
- Muscle weakness or limpness
- Confusion or drowsiness
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, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor identify potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your current medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor identify potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your current medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all 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
- Abdominal pain
- Lethargy
- Drowsiness
- Muscle weakness
- Hypotension (low blood pressure)
- Bradycardia (slow heart rate)
- Depressed deep tendon reflexes
- Respiratory depression
- Coma
- Cardiac arrest
What to Do:
Immediately seek emergency medical attention. Call 911 or Poison Control at 1-800-222-1222. Treatment may involve intravenous calcium (to antagonize magnesium effects), forced diuresis, and in severe cases, hemodialysis.
Drug Interactions
Contraindicated Interactions
- Sodium Polystyrene Sulfonate (Kayexalate) - risk of intestinal necrosis
- Patiromer (Veltassa) - binds to magnesium, reducing its absorption
Major Interactions
- Bisphosphonates (e.g., Alendronate, Risedronate) - reduced absorption of bisphosphonate
- Tetracyclines (e.g., Doxycycline, Minocycline) - reduced absorption of tetracycline
- Fluoroquinolones (e.g., Ciprofloxacin, Levofloxacin) - reduced absorption of fluoroquinolone
- Thyroid Hormones (e.g., Levothyroxine) - reduced absorption of thyroid hormone
- Mycophenolate - reduced absorption of mycophenolate
- Digoxin - altered absorption and potential for arrhythmias with hypermagnesemia
- Calcium Channel Blockers (e.g., Amlodipine, Diltiazem) - additive hypotensive and CNS depressant effects with hypermagnesemia
- Neuromuscular Blockers (e.g., Vecuronium, Rocuronium) - enhanced neuromuscular blockade
Moderate Interactions
- Potassium-sparing diuretics (e.g., Spironolactone, Amiloride) - increased risk of hypermagnesemia in renal impairment
- Other laxatives - additive laxative effect, increased risk of diarrhea and electrolyte imbalance
- Iron supplements - reduced iron absorption
- Zinc supplements - reduced zinc absorption
- H2-receptor antagonists (e.g., Ranitidine, Famotidine) - may alter absorption of magnesium
- Proton Pump Inhibitors (e.g., Omeprazole, Pantoprazole) - may alter absorption of magnesium
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Renal Function (BUN, Creatinine, eGFR)
Rationale: Magnesium is primarily renally excreted; impaired renal function increases risk of hypermagnesemia.
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 has risk factors for hypermagnesemia.
Timing: Before initiating high-dose or chronic therapy, or in patients with renal impairment.
Routine Monitoring
Serum Magnesium Levels
Frequency: Periodically (e.g., weekly to monthly) for chronic high-dose therapy 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; >4.9 mg/dL (2.0 mmol/L) is severe hypermagnesemia requiring urgent intervention.
Bowel Habits/Frequency
Frequency: Daily (for laxative use)
Target: Regular, soft bowel movements
Action Threshold: Excessive diarrhea, abdominal cramping, or no bowel movement after appropriate time.
Symptoms of Hypermagnesemia
Frequency: Daily, especially with high doses or renal impairment.
Target: Absence of symptoms
Action Threshold: Muscle weakness, lethargy, nausea, vomiting, hypotension, bradycardia, depressed reflexes.
Symptom Monitoring
- Diarrhea
- Abdominal cramping
- Nausea
- Vomiting
- Muscle weakness
- Lethargy
- Drowsiness
- Confusion
- Hypotension
- Bradycardia
- Depressed deep tendon reflexes
- Respiratory depression (severe hypermagnesemia)
Special Patient Groups
Pregnancy
Generally considered safe for occasional use as an antacid or laxative during pregnancy, particularly in the second and third trimesters. However, high doses or chronic use should be avoided due to the potential for hypermagnesemia in the mother and fetus, especially near term. Consult a healthcare provider.
Trimester-Specific Risks:
First Trimester:
Low risk; generally considered safe for occasional use.
Second Trimester:
Low risk; generally considered safe for occasional use.
Third Trimester:
Low risk for occasional use, but caution with high doses or chronic use due to potential for neonatal hypermagnesemia (e.g., hypotonia, respiratory depression) if used close to delivery.
Lactation
Magnesium is a normal component of breast milk. Oral magnesium oxide is considered compatible with breastfeeding when used at recommended doses. Infant exposure is low, and adverse effects are unlikely.
Infant Risk:
Low risk (L1)
Pediatric Use
Use as a laxative in children under 6 years should only be under medical supervision. Dosing for magnesium supplementation should be carefully determined by a physician based on age, weight, and magnesium status. Risk of hypermagnesemia is higher in infants and young children, especially with renal impairment.
Geriatric Use
Elderly patients may have age-related decline in renal function, increasing their risk of hypermagnesemia. Lower doses may be necessary, and close monitoring of renal function and serum magnesium levels is recommended. They may also be more susceptible to the laxative effects and dehydration.
Clinical Information
Clinical Pearls
- Magnesium oxide has a lower elemental magnesium content per milligram compared to some other magnesium salts (e.g., magnesium citrate, magnesium glycinate), but its high concentration in tablets makes it a common choice for supplementation.
- For laxative use, ensure adequate fluid intake to maximize efficacy and prevent dehydration.
- Advise patients to separate administration of magnesium oxide from other medications by at least 2-4 hours to minimize drug interactions, especially with antibiotics, bisphosphonates, and thyroid hormones.
- Patients with kidney disease should avoid magnesium oxide unless specifically directed and closely monitored by a physician due to the high risk of hypermagnesemia.
- While generally safe, excessive or chronic use can lead to hypermagnesemia, particularly in vulnerable populations. Educate patients on symptoms of hypermagnesemia.
Alternative Therapies
- For Magnesium Supplementation: Magnesium citrate, Magnesium glycinate, Magnesium L-threonate, Magnesium sulfate (IV/IM).
- For Antacid: Calcium carbonate, Aluminum hydroxide, Sodium bicarbonate, H2-receptor antagonists (e.g., Famotidine), Proton pump inhibitors (e.g., Omeprazole).
- For Laxative: Polyethylene glycol (PEG), Docusate sodium, Senna, Bisacodyl, Lactulose, Psyllium.
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets
Generic Available:
Yes
Insurance Coverage:
Usually covered as an OTC or generic prescription, often Tier 1 or 2.
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 your 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 emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.