Magnesium 500mg 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, Osmotic; Antacid
Pharmacologic Class
Electrolyte; Osmotic agent; 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 with magnesium deficiency. It also works as a laxative to relieve constipation by drawing water into the intestines, and as an antacid to reduce stomach acid. It's important to take it as directed and be aware of potential side effects, especially if you have kidney problems.
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. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to 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. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to 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
- Maintain adequate hydration, especially when using as a laxative.
- Follow a balanced diet rich in magnesium (e.g., leafy greens, nuts, seeds, whole grains).
- Do not exceed recommended doses without consulting a healthcare professional.
- Separate administration from certain medications (e.g., some antibiotics, thyroid hormones) by at least 2-4 hours.
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:
For magnesium deficiency: 250-500 mg Magnesium Oxide once or twice daily. For constipation: 1000-2000 mg Magnesium Oxide once daily or in divided doses.
Dose Range:
250 - 2000 mg
Condition-Specific Dosing:
Magnesium Deficiency:
250-500 mg Magnesium Oxide 1-2 times daily
Constipation:
1000-2000 mg Magnesium Oxide at bedtime or in divided doses
Antacid:
250-500 mg Magnesium Oxide as needed
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established (use with extreme caution, only under medical supervision)
Child:
6-11 years: For constipation, 400-800 mg Magnesium Oxide once daily.
Adolescent:
12-17 years: For constipation, 1000-2000 mg Magnesium Oxide once daily.
Dose Adjustments
Renal Impairment:
Mild:
Use with caution, monitor magnesium levels.
Moderate:
Reduce dose by 50% or avoid. Monitor magnesium levels closely.
Severe:
Contraindicated (CrCl < 30 mL/min) due to high risk of hypermagnesemia.
Dialysis:
Contraindicated.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed.
Pharmacology
Mechanism of Action
Magnesium is an essential mineral and cofactor for over 300 enzymatic reactions, including protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation. 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.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 4-10% (elemental magnesium from magnesium oxide), highly variable.
Tmax:
2-6 hours (for systemic absorption of elemental magnesium); laxative effect onset typically 0.5-6 hours.
FoodEffect:
Food may slightly decrease absorption but can reduce GI upset.
Distribution:
Vd:
Not well-defined; widely distributed throughout the body (50-60% in bone, 20-25% in muscle, 1% in extracellular fluid).
ProteinBinding:
Approximately 25-30% bound to plasma proteins.
CnssPenetration:
Limited, but essential for neurological function.
Elimination:
HalfLife:
Approximately 20-24 hours (intracellular magnesium); plasma half-life is shorter.
Clearance:
Primarily renal.
ExcretionRoute:
Primarily renal (absorbed magnesium); unabsorbed portion excreted in feces.
Unchanged:
Most absorbed magnesium is excreted unchanged in urine.
Pharmacodynamics
OnsetOfAction:
Laxative effect: 0.5-6 hours; Antacid effect: immediate.
PeakEffect:
Laxative effect: 6-12 hours; Antacid effect: within minutes.
DurationOfAction:
Laxative effect: variable; Antacid effect: 30 minutes to 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:
- 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. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
- Diarrhea
Important Note: This list does not include all possible side effects. If you have questions or 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:
- 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. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
- Diarrhea
Important Note: This list does not include all possible side effects. If you have questions or 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:
- Signs of too much magnesium (hypermagnesemia): Severe diarrhea, profound muscle weakness, lethargy, confusion, significant drop in blood pressure, slow or irregular heartbeat, difficulty breathing.
- Signs of allergic reaction: Rash, itching, swelling (especially of face/tongue/throat), severe dizziness, trouble breathing.
- Persistent constipation or worsening symptoms despite 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 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 is crucial because this medication may interact with other drugs or exacerbate existing health problems.
* Any health issues you are experiencing, as they may affect the safety and efficacy of this medication.
To ensure your safety, it is vital to verify that it is safe to take this medication with all your other 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, 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 is crucial because this medication may interact with other drugs or exacerbate existing health problems.
* Any health issues you are experiencing, as they may affect the safety and efficacy of this medication.
To ensure your safety, it is vital to verify that it is safe to take this medication with all your other 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 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 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
- Profound muscle weakness
- Lethargy
- Confusion
- Significant drop in blood pressure (hypotension)
- Slow or irregular heartbeat (bradycardia)
- Respiratory depression
- Coma
- Cardiac arrest
What to Do:
Immediately call emergency services (e.g., 911 in the US) or a poison control center (1-800-222-1222). Treatment may involve intravenous calcium (to antagonize magnesium effects), forced diuresis, and in severe cases, hemodialysis.
Drug Interactions
Major Interactions
- Tetracyclines (e.g., doxycycline, minocycline): Chelation, significantly reduced absorption. Separate administration by at least 2-4 hours.
- Fluoroquinolones (e.g., ciprofloxacin, levofloxacin): Chelation, significantly reduced absorption. Separate administration by at least 2-4 hours.
- Potassium-sparing diuretics (e.g., amiloride, spironolactone): Increased risk of hypermagnesemia, especially in renal impairment.
Moderate Interactions
- Bisphosphonates (e.g., alendronate): Reduced absorption. Separate administration by at least 30 minutes to 2 hours.
- Thyroid hormones (e.g., levothyroxine): Reduced absorption. Separate administration by at least 4 hours.
- Iron supplements: Reduced absorption of iron. Separate administration by 2 hours.
- Calcium channel blockers (e.g., nifedipine, amlodipine): May enhance hypotensive effects.
- Neuromuscular blockers (e.g., rocuronium, succinylcholine): May potentiate their effects, leading to prolonged paralysis.
Minor Interactions
- Digoxin: High magnesium levels can interfere with digoxin's effects.
- Antacids (aluminum/calcium-containing): May alter absorption of magnesium.
Monitoring
Baseline Monitoring
Renal function (serum creatinine, eGFR)
Rationale: Magnesium is primarily renally excreted; impaired renal function increases hypermagnesemia risk.
Timing: Before initiating therapy, especially in elderly or those with known renal issues.
Serum Magnesium levels
Rationale: To establish baseline and guide dosing, particularly if deficiency is suspected or high doses are planned.
Timing: Before initiation, if clinically indicated.
Routine Monitoring
Serum Magnesium levels
Frequency: Periodically, especially in patients with renal impairment, those receiving high doses, or experiencing symptoms.
Target: 1.7-2.2 mg/dL (0.7-0.9 mmol/L)
Action Threshold: >2.5 mg/dL (mild hypermagnesemia); >4.8 mg/dL (moderate-severe hypermagnesemia) requires dose reduction or discontinuation.
Bowel movements
Frequency: Daily (for laxative use).
Target: Regular, soft stools.
Action Threshold: Diarrhea (reduce dose); continued constipation (increase dose or consider alternative).
Symptom Monitoring
- Diarrhea
- Abdominal cramping
- Nausea
- Vomiting
- Muscle weakness
- Lethargy
- Confusion
- Dizziness
- Hypotension
- Bradycardia
- Respiratory depression (signs of hypermagnesemia)
Special Patient Groups
Pregnancy
Generally considered safe for use as a supplement or occasional laxative at recommended doses. Magnesium is an essential mineral during pregnancy. However, high doses (e.g., for pre-eclampsia) are administered under strict medical supervision due to potential for maternal and fetal toxicity.
Trimester-Specific Risks:
First Trimester:
Low risk at recommended doses.
Second Trimester:
Low risk at recommended doses.
Third Trimester:
Low risk at recommended doses. Avoid excessive doses close to delivery due to potential for neonatal hypotonia or respiratory depression.
Lactation
Considered safe. Magnesium is a normal component of breast milk. Oral magnesium oxide is poorly absorbed by the mother, and only small amounts pass into breast milk, posing low risk to the infant.
Infant Risk:
Low risk.
Pediatric Use
Use with caution. Dosing must be carefully adjusted by age and weight. Risk of hypermagnesemia is higher in infants and young children, especially with renal impairment. Not recommended for infants without medical supervision.
Geriatric Use
Increased risk of hypermagnesemia due to age-related decline in renal function. Start with lower doses and monitor renal function and magnesium levels closely. More susceptible to adverse effects like diarrhea and dehydration.
Clinical Information
Clinical Pearls
- Magnesium oxide has a relatively low bioavailability compared to other magnesium salts (e.g., citrate, aspartate), making it more effective as a laxative due to its osmotic properties in the gut.
- Patients should be advised to separate administration from certain antibiotics (tetracyclines, fluoroquinolones) and other medications by at least 2-4 hours to prevent reduced absorption of those medications.
- Crucial to monitor for signs of hypermagnesemia, especially in patients with impaired kidney function, as magnesium is primarily renally excreted.
- Not suitable for long-term use as a laxative without medical advice, as it can lead to electrolyte imbalances or dependency.
Alternative Therapies
- For magnesium deficiency: Magnesium citrate, magnesium glycinate, magnesium L-threonate.
- For constipation: Psyllium (bulk-forming), polyethylene glycol (osmotic), docusate (stool softener), senna (stimulant).
- For antacid: Calcium carbonate, aluminum hydroxide, H2 blockers (e.g., famotidine), PPIs (e.g., omeprazole).
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets
Generic Available:
Yes
Insurance Coverage:
Often OTC, may not be covered by prescription plans unless prescribed for a specific medical condition. If covered, typically Tier 1 or 2.
General Drug Facts
If your symptoms or health issues persist or worsen, it is 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 it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with 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 detailed information about the overdose, including the medication taken, the amount, and the time it occurred.