Mag-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
Laxative, Antacid, Magnesium Supplement
Pharmacologic Class
Osmotic Laxative, Antacid (neutralizing agent), Mineral Supplement
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 a laxative to treat occasional constipation or as an antacid to relieve heartburn and indigestion. It works by drawing water into the intestines to help with bowel movements, or by neutralizing stomach acid.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. 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
Store your 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 by your pharmacist. Instead, check with your pharmacist for guidance on the proper disposal method or explore drug take-back programs in your area.
What to Do If You Miss 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 get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. 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
Store your 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 by your pharmacist. Instead, check with your pharmacist for guidance on the proper disposal method or explore drug take-back programs in your area.
What to Do If You Miss 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 (at least 6-8 glasses of water daily) when using as a laxative to prevent dehydration and aid effectiveness.
- Maintain a balanced diet rich in fiber to support regular bowel movements.
- Avoid taking other medications within 2 hours before or after magnesium oxide, especially antibiotics (tetracyclines, fluoroquinolones), bisphosphonates, and thyroid hormones, as it can interfere with their absorption.
- Do not use for more than 7 days for constipation or 14 days for antacid use without consulting a doctor.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
For constipation: 2-4 tablets (800-1600 mg) once daily at bedtime or in divided doses. For antacid: 1-2 tablets (400-800 mg) as needed, up to 4 times daily. For magnesium deficiency: 1-2 tablets (400-800 mg) 1-2 times daily.
Dose Range:
400 - 1600 mg
Condition-Specific Dosing:
constipation:
800-1600 mg daily
antacid:
400-800 mg up to 4 times daily
magnesium_deficiency:
400-800 mg 1-2 times daily
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
For constipation (6-11 years): 1-2 tablets (400-800 mg) once daily. For antacid (6-11 years): 1 tablet (400 mg) as needed, up to 4 times daily. Dosing for magnesium deficiency should be guided by a physician.
Adolescent:
Similar to adult dosing for constipation and antacid. For magnesium deficiency, consult a physician.
Dose Adjustments
Renal Impairment:
Mild:
Use with caution; monitor serum magnesium.
Moderate:
Reduce dose by 50% or avoid; monitor serum magnesium closely.
Severe:
Contraindicated due to risk of hypermagnesemia.
Dialysis:
Contraindicated due to risk of hypermagnesemia; magnesium is removed by dialysis, but accumulation can occur between sessions.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed.
Pharmacology
Mechanism of Action
As a laxative, magnesium oxide acts as an osmotic agent, drawing water into the intestinal lumen, which increases stool volume and stimulates peristalsis. As an antacid, it neutralizes gastric acid by reacting with hydrochloric acid to form magnesium chloride and water. As a magnesium supplement, it provides an exogenous source of magnesium, an essential cation involved in numerous enzymatic reactions, nerve and muscle function, and bone formation.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 4-10% (as a supplement); very low for laxative/antacid effect as it's designed to stay in the GI tract.
Tmax:
Variable, typically 2-6 hours for systemic absorption.
FoodEffect:
Food may slightly delay absorption but does not significantly alter the extent of absorption.
Distribution:
Vd:
Not readily quantifiable for magnesium; widely distributed throughout the body, with approximately 50-60% in bone, 39-49% in intracellular fluid, and 1% in extracellular fluid.
ProteinBinding:
Approximately 30% (bound to albumin).
CnssPenetration:
Limited under normal conditions; increased with hypermagnesemia.
Elimination:
HalfLife:
Approximately 20-24 hours (for absorbed magnesium, dependent on renal function).
Clearance:
Primarily renal clearance.
ExcretionRoute:
Renal (absorbed magnesium); Fecal (unabsorbed magnesium).
Unchanged:
Nearly 100% of absorbed magnesium is excreted unchanged.
Pharmacodynamics
OnsetOfAction:
Antacid: Within minutes. Laxative: 30 minutes to 6 hours.
PeakEffect:
Antacid: 30-60 minutes. Laxative: 6-12 hours.
DurationOfAction:
Antacid: 1-3 hours. Laxative: Variable, depending on dose and individual response.
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:
- 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, or swelling of the mouth, face, lips, tongue, or throat.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. Contact your doctor if you experience:
- Diarrhea
or if any other side effects bother you or do not go away.
Reporting Side Effects
This list does not include all possible side effects. If you have questions or concerns about side effects, consult your doctor for medical advice. 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:
- 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, or swelling of the mouth, face, lips, tongue, or throat.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. Contact your doctor if you experience:
- Diarrhea
or if any other side effects bother you or do not go away.
Reporting Side Effects
This list does not include all possible side effects. If you have questions or concerns about side effects, consult your doctor for medical advice. 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 diarrhea or persistent diarrhea
- Severe abdominal pain or cramping
- Rectal bleeding
- No bowel movement after several days of laxative use
- Signs of too much magnesium (hypermagnesemia): unusual tiredness, muscle weakness, slow heartbeat, dizziness, confusion, difficulty breathing.
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 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 health problems you have, as they may affect the safety and efficacy of this medication.
To ensure your safety, it is crucial to:
Discuss all your medications and health problems with your doctor and pharmacist to verify that it is safe to take this medication in conjunction with your other treatments.
* Avoid starting, stopping, or changing the dose of any medication without first consulting your doctor. This precaution will help prevent potential interactions and ensure the safe use of this 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 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 health problems you have, as they may affect the safety and efficacy of this medication.
To ensure your safety, it is crucial to:
Discuss all your medications and health problems with your doctor and pharmacist to verify that it is safe to take this medication in conjunction with your other treatments.
* Avoid starting, stopping, or changing the dose of any medication without first consulting your doctor. This precaution will help prevent potential interactions and ensure the safe use of this medication.
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 the prescribed duration of treatment and do not take this drug for longer than recommended by your doctor. If you are pregnant, planning to become pregnant, or are 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:
- Nausea
- Vomiting
- Diarrhea
- Flushing
- Muscle weakness
- Lethargy
- Hypotension
- Bradycardia
- Respiratory depression
- Coma
- Cardiac arrest
What to Do:
If you suspect an overdose, seek immediate medical attention or call a poison control center (1-800-222-1222). Treatment may involve intravenous fluids, diuretics to promote magnesium excretion, and in severe cases, calcium gluconate to counteract cardiac effects.
Drug Interactions
Contraindicated Interactions
- Sodium polystyrene sulfonate (Kayexalate) - risk of intestinal necrosis
Major Interactions
- Bisphosphonates (e.g., alendronate, risedronate) - decreased absorption of bisphosphonate
- Tetracyclines (e.g., doxycycline, minocycline) - decreased absorption of tetracycline
- Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) - decreased absorption of fluoroquinolone
- Thyroid hormones (e.g., levothyroxine) - decreased absorption of thyroid hormone
- Mycophenolate mofetil - decreased absorption of mycophenolate
Moderate Interactions
- Potassium-sparing diuretics (e.g., spironolactone, amiloride) - increased risk of hypermagnesemia
- Calcium channel blockers (e.g., amlodipine, diltiazem) - additive hypotensive effects, increased risk of AV block
- Neuromuscular blockers (e.g., rocuronium, succinylcholine) - enhanced neuromuscular blockade
- Digoxin - altered absorption, potential for altered cardiac effects
- Iron supplements - decreased absorption of iron
Minor Interactions
- Other antacids - additive effects
- Laxatives - additive effects
Monitoring
Baseline Monitoring
Renal function (BUN, creatinine)
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, especially if treating deficiency or in patients at risk of hypermagnesemia.
Timing: Before initiating therapy for deficiency or in high-risk patients.
Routine Monitoring
Serum magnesium levels
Frequency: Periodically (e.g., weekly to monthly) if on long-term therapy, high doses, or with impaired renal function.
Target: 1.5-2.5 mg/dL (0.6-1.0 mmol/L)
Action Threshold: If >2.5 mg/dL, consider dose reduction or discontinuation; if >4.0 mg/dL, immediate intervention for hypermagnesemia.
Renal function (BUN, creatinine)
Frequency: Periodically (e.g., every 3-6 months) if on long-term therapy or with changing clinical status.
Target: Normal limits
Action Threshold: Significant decline warrants dose adjustment or discontinuation of magnesium.
Bowel movements (for laxative use)
Frequency: Daily
Target: Regular, soft stools
Action Threshold: Persistent diarrhea or no bowel movement after 3-7 days may require dose adjustment or re-evaluation.
Symptom Monitoring
- Diarrhea
- Abdominal cramping
- Nausea
- Vomiting
- Muscle weakness
- Lethargy
- Dizziness
- Hypotension
- Bradycardia
- Respiratory depression (signs of hypermagnesemia)
Special Patient Groups
Pregnancy
Generally considered safe for occasional use during pregnancy for constipation or antacid purposes, but high doses or prolonged use should be avoided due to potential for hypermagnesemia in the mother and fetus, especially near term. Consult a healthcare provider.
Trimester-Specific Risks:
First Trimester:
Low risk with occasional use.
Second Trimester:
Low risk with occasional use.
Third Trimester:
Increased caution, especially with high doses or prolonged use, due to potential for hypermagnesemia in the neonate (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, as only small amounts are absorbed systemically by the mother and transferred to breast milk. Monitor infant for diarrhea.
Infant Risk:
Low risk; monitor for loose stools or diarrhea in the infant.
Pediatric Use
Use with caution in children, especially those under 6 years old. Dosing should be age-appropriate and for short-term use only. Prolonged use or high doses can lead to electrolyte imbalances. Always consult a pediatrician before use in infants and young children.
Geriatric Use
Elderly patients are more susceptible to renal impairment, which increases the risk of hypermagnesemia. Start with lower doses and monitor renal function and serum magnesium levels closely. They may also be more prone to dehydration with laxative use.
Clinical Information
Clinical Pearls
- Magnesium oxide has a relatively low systemic bioavailability when used as a laxative/antacid, but significant absorption can occur, especially with higher doses or prolonged use, leading to hypermagnesemia, particularly in patients with impaired renal function.
- Advise patients to separate administration of magnesium oxide from other medications by at least 2 hours to minimize drug interactions due to chelation or altered gastric pH.
- For constipation, ensure adequate fluid intake to maximize the osmotic effect and prevent dehydration.
- Magnesium oxide is often preferred for magnesium supplementation due to its high elemental magnesium content per dose, but other forms (e.g., citrate, glycinate) may have better bioavailability or be better tolerated for GI side effects.
- Patients should be advised not to exceed recommended doses or use for prolonged periods without medical supervision.
Alternative Therapies
- For constipation: polyethylene glycol (MiraLAX), docusate sodium (Colace), senna, bisacodyl, psyllium (Metamucil), lactulose.
- For antacid: calcium carbonate (Tums), aluminum hydroxide/magnesium hydroxide (Maalox, Mylanta), famotidine (Pepcid AC), ranitidine (Zantac 360), omeprazole (Prilosec OTC).
- For magnesium deficiency: magnesium citrate, magnesium glycinate, magnesium aspartate, magnesium chloride.
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets
Generic Available:
Yes
Insurance Coverage:
Generally not covered by insurance as an over-the-counter (OTC) product, unless prescribed by a physician and covered under specific plans (e.g., FSA/HSA eligible).
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 occurred.