If you are currently being treated with any of the following medications, you should not use magnesium without first talking to your health care provider.

Antibiotics -- The absorption of quinolone antibiotics, such as ciprofloxacin (Cipro) and moxifloxacin (Avelox), tetracycline antibiotics, including tetracycline (Sumycin), doxycycline (Vibramycin), and minocycline (Minocin), and nitrofurantoin (Macrodandin), may be diminished when taking magnesium supplements. Therefore, magnesium should be taken 1 hour before or 2 hours after taking these medications to avoid interference with absorption.

Blood Pressure Medications, Calcium Channel Blockers -- Magnesium may increase the likelihood 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 amlodipine (Norvasc), diltiazem (Cardizem), felodipine (Plendil), and verapamil (Calan).

Diabetic Medications -- Magnesium hydroxide, commonly found in antacids such as Alternagel, may increase the absorption of glipizide and glyburide, medications used to control blood sugar levels. Ultimately, this may prove to allow for reduction in the dosage of those medications.

Digoxin -- It is important that normal levels of magnesium be maintained while taking digoxin (Lanoxin) because low blood levels of magnesium can increase adverse effects from this drug, including heart palpitations and nausea. In addition, digoxin can lead to increased loss of magnesium in the urine. A health care provider will follow magnesium levels closely to determine whether magnesium supplementation is necessary in individuals taking digoxin.

Diuretics -- Two types of diuretics known as loop (such as furosemide or Lasix) and thiazide (including hydrochlorothiazide) can deplete magnesium levels. For this reason, doctors who prescribe diuretics may consider recommending magnesium supplements as well.

Hormone Replacement Therapy for menopause -- 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.

Levothyroxine -- There have been case reports of magnesium containing antacids reducing the effectiveness of levothyroxine, which is taken for an under active thyroid. This is important because many people take laxatives containing magnesium without letting their doctor know.

Penicillamine -- Penicillamine, a medication used for the treatment of 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. Even with this relative inactivation, however, supplementation with magnesium and other nutrients by those taking penicillamine may reduce side effects associated with this medication. A health care provider can determine whether magnesium supplements are safe and appropriate if you are taking penicillamine.

Tiludronate and Alendronate -- Magnesium may interfere with absorption of medications used in osteoporosis, including alendronate (Fosamax). Magnesium supplements or magnesium-containing antacids should be taken at least 1 hour before or 2 hours after taking these medications to minimize potential interference with absorption.

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.