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

Antibiotics
The absorption of quinolone antibiotics (such as ciprofloxacin and moxofloxacin), tetracycline antibiotics (including tetracycline, doxycycline, and minocycline), and nitrofurantoin is diminished when taken with magnesium supplements. Therefore, magnesium should be taken two to four hours before or 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) in pregnant women. Other calcium channel blockers include amlodipine, diltiazem, felodipine, and verapamil.

Diabetic Medications
Magnesium hydroxide, commonly found in antacids, 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 because low blood levels of magnesium can increase adverse effects from this drug. In addition, digoxin can lead to increased loss of magnesium in the urine. A healthcare provider will follow magnesium levels closely to determine whether magnesium supplementation is necessary.

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

Hormone Replacement Therapy for menopause
Magnesium levels tend to decrease during menopause. 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 healthcare 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 healthcare practitioner can determine whether magnesium supplements are safe and appropriate if you are taking penicillamine.

Tiludronate and Alendronate
Magnesium may interfere with absorption of tiludronate, a medication similar to alendronate that is used for the treatment of osteoporosis. This interaction has not been reported with alendronate specifically. Magnesium supplements or magnesium-containing antacids should be taken at least two hours before or two 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, antacids, and insulin may lower magnesium levels. Please refer to the depletions monographs on some of these medications for more information.