These medicines interact with magnesium

Magnesium assists with the absorption of thiamine (vitamin B1) in the body, but can have side effects when taken with certain medicines. The following detailed description of undesirable side effects for magnesium with certain medications has been compiled by an expert. Always first consult your doctor before taking any supplement! 

Antibiotics (aminoglycoside antibiotics)

Some antibiotics can affect the muscles. These antibiotics are called aminoglycosides. Magnesium can also affect the muscles. Taking these antibiotics and getting a magnesium shot might cause muscle problems.
Some aminoglycoside antibiotics include amikacin (Amikin), gentamicin (Garamycin), kanamycin (Kantrex), streptomycin, tobramycin (Nebcin) and others.

Antibiotics (quinolone antibiotics)

Magnesium might decrease how much antibiotic the body absorbs. Taking magnesium along with some antibiotics might decrease the effectiveness of some antibiotics. To avoid this interaction, take these antibiotics at least 2 hours before, or 4 to 6 hours after, magnesium supplements.
Some of these antibiotics that might interact with magnesium include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan) and grepafloxacin (Raxar).

Antibiotics (tetracycline antibiotics)

Magnesium can attach to tetracyclines in the stomach. This decreases the amount of tetracyclines that the body can absorb. Taking magnesium along with tetracyclines might decrease the effectiveness of tetracyclines. To avoid this interaction, take calcium 2 hours before or 4 hours after taking tetracyclines.
Some tetracyclines include demeclocycline (Declomycin), minocycline (Minocin) and tetracycline (Achromycin).

Bisphosphonates

Magnesium can decrease how much bisphosphate the body absorbs. Taking magnesium along with bisphosphates can decrease the effectiveness of bisphosphate. To avoid this interaction, take bisphosphonate at least two hours before magnesium or later in the day.
Some bisphosphonates include alendronate (Fosamax), etidronate (Didronel), risedronate (Actonel), tiludronate (Skelid) and others.

Medications for high blood pressure (calcium channel blockers)

Magnesium might decrease blood pressure. Taking magnesium with medication for high blood pressure might cause your blood pressure to go too low.
Some medications for high blood pressure include nifedipine (Adalat, Procardia), verapamil (Calan, Isoptin, Verelan), diltiazem (Cardizem), isradipine (DynaCirc), felodipine (Plendil), amlodipine (Norvasc, Lomanor, Calbloc) and others.

Muscle relaxants

Magnesium seems to help relax muscles. Taking magnesium along with muscle relaxants can increase the risk of side effects of muscle relaxants.
Some muscle relaxants include carisoprodol (Soma), pipecuronium (Arduan), orphenadrine (Banflex, Disipal), cyclobenzaprine, gallamine (Flaxedil), atracurium (Tracrium), pancuronium (Pavulon), succinylcholine (Anectine) and others.

“Water pills” (potassium-sparing diuretics)

Some "water pills" can increase magnesium levels in the body. Taking some water pills along with magnesium might cause an excess of magnesium in the body.
Some water pills that increase magnesium in the body include amiloride (Midamor), spironolactone (Aldactone) and triamterene (Dyrenium).