Magnesium can decrease the absorption and effectiveness of numerous medications, including some common antibiotics such as tetracycline (Achromycin, Sumycin), demeclocycline (Declomycin), doxycycline (Vibramycin), minocycline (Minocin), ciprofloxacin (Cipro), levofloxacin (Levaquin), moxifloxacin (Avelox) and ofloxacin (Floxin); certain statin drugs such as rosuvastatin (Crestor) and atorvastatin (Lipitor); sotalol (Betapace, Sotylize, Sorine), a drug prescribed for atrial fibrillation; gabapentin (Neurontin), a drug prescribed for seizures; and levothyroxine (Synthroid), a drug prescribed for thyroid disorders. On the other hand, one form of magnesium may increase the absorption of certain anti-diabetes drugs such as glibenclamide (DiaBeta, Micronase, Glynase) and glimepiride (Amaryl), potentially affecting blood sugar control. In some cases, magnesium can still be taken, but only several hours before or after taking these drugs.
Be aware that these interactions apply not only to magnesium in supplements but also in over-the-counter antacids and laxatives.
In addition, certain medications such as the immunosuppressant drug tacrolimus, oral contraceptives, estrogen replacement therapy, and loop and thiazide diuretics can deplete levels of magnesium in the body, while antacid medications including H2 blockers such as cimetidine (Tagamet), famotidine (Pepcid AC) and ranitidine (Zantac), and proton pump inhibitors such as esomeprazole (Nexium) and lansoprazole (Prevacid), may interfere with magnesium's laxative effects.
For details, see the Cautions and Concerns section of the Magnesium Supplements Review.