Aminoglycosides: Use with magnesium may cause neuromuscular weakness and paralysis.
Antibiotics: Taking magnesium supplements may reduce the absorption of quinolone antibiotics, tetracycline antibiotics, and nitrofurantoin (Macrodandin). Magnesium should be taken 1 hour before or 2 hours after taking these medications. Quinolone and tetracycline antibiotics include: Ciprofloxacin (Cipro), Moxifloxacin (Avelox), Tetracycline (Sumycin), Doxycycline (Vibramycin), Minocycline (Minocin).
Blood Pressure Medications, Calcium Channel Blockers: Magnesium may increase the risk of negative side effects (such as dizziness, nausea, and fluid retention) from calcium channel blockers (particularly nifedipine or Procardia) in pregnant women. Other calcium channel blockers include: Aamlodipine (Norvasc), Diltiazem (Cardizem), Felodipine (Plendil) and Verapamil (Calan)
Medications for diabetes: Magnesium hydroxide, commonly found in antacids such as Alternagel, may increase the absorption of some medications used to control blood sugar levels (particularly glipizide or Glucatrol and glyburide or Micronase). If you take these medications to control blood sugar, your doctor may need to adjust your dose.
Digoxin (Lanoxin): Low blood levels of magnesium can increase negative effects from digoxin, including heart palpitations and nausea. In addition, digoxin can cause more magnesium to be lost in the urine. A doctor will monitor magnesium levels in people taking digoxin to see whether they need a magnesium supplement.
Diuretics: Diuretics known as loop (such as furosemide or Lasix) and thiazide (including hydrochlorothiazide) can lower magnesium levels. For this reason, doctors who prescribe diuretics may recommend magnesium supplements as well.
Fluoroquinones: Use with magnesium may decrease absorption and effectiveness. Flouroquinones should be taken a minimum of 4 hours before any products containing magnesium.
Hormone Replacement Therapy: Magnesium levels tend to decrease during menopause. Clinical studies suggest, however, that hormone replacement therapy may help prevent the loss of this mineral. Postmenopausal women, or those taking hormone replacement therapy, should talk with a health care provider about the risks and benefits of magnesium supplementation.
Labetol: Use with magneisum can slow heart beat abnormally and reduce cardiac output.
Levomethadyl: Use with magnesium may precipitate a heart condition called QT prolongation.
Levothyroxine: There have been case reports of magnesium containing antacids reducing the effectiveness of levothyroxine, a medication that treats underactive thyroid.
Penicillamine: A medication used to treat Wilson’s disease (a condition characterized by high levels of copper in the body) and rheumatoid arthritis, can inactivate magnesium, particularly when high doses of the drug are used over a long period of time. Supplementation with magnesium and other nutrients may reduce side effects associated with penicillamine. If you take penicillamine, a health care provider can determine whether magnesium supplements are right for you.
Tiludronate (Skelid) and Alendronate (Fosamax): Magnesium may interfere with absorption of medications used in osteoporosis, including alendronate (Fosamax). Magnesium or antacids containing magnesium should be taken 1 hour before or 2 hours after taking these medications.
Others: Aminoglycoside antibiotics (such as gentamicin and tobramycin), thiazide diuretics (such as hydrochlorothiazide), loop diuretics (such as furosemide and bumetanide), amphotericin B, corticosteroids (prednisone or Deltasone), antacids, and insulin may lower magnesium levels. Please refer to the depletions monographs on some of these medications for more information.
Source: “Magnesium.”,University of Maryland Medical Center, [accessed: 20.07.2011], http://www.umm.edu/altmed/articles/magnesium-000313.htm