Magnesium glycerophosphate is a dietary supplement taken by those with low levels of the mineral magnesium. Healthy levels of this mineral help proper digestion and are essential for good nutrition, strong bones and nerve function. Daily doses of less than 350 mg of magnesium are generally considered to be safe for adults; however, large amounts of magnesium may cause serious side effects when taken in combination with certain medications or by those with certain conditions.
Taking magnesium together with certain antibiotics can affect the body's ability to absorb the medication and reduce the effectiveness of treatment. Antibiotics known to have decreased potency when combined with magnesium supplements include tetracycline and quinolone antibiotics that are often used to treat respiratory, sinus and urinary tract infections. Injections of aminoglycoside, an antibiotic used to treat severe bacterial infections, can also affect muscle function and cause muscle twitches, convulsion and even seizures when taken with magnesium.
Some patients suffering from osteoporosis and similar diseases are given a medication called "bisphosphonates" to prevent the loss of bone mass. WebMD recommends that commonly prescribed bisphosphonates such as alendronate (Fosamax), etidronate (Didronel) and risedronate (Actonel) be taken at least two hours before magnesium to ensure proper absorption of the medication.
Taking muscle relaxants together with magnesium can increase the adverse effects associated with muscle relaxers such as blurry vision, lightheadedness, drowsiness and dizziness.
Digesting water pills such as amiloride (Midamor), spironolactone (Aldactone) and triamterene (Dyrenium) can increase magnesium to dangerous levels when taken with magnesium supplements like magnesium glycerophosphate.
High Blood Pressure
Magnesium can decrease blood pressure to an abnormally low level when taken with high blood pressure medications such as nifedipine (Adalat, Procardia), diltiazem (Cardizem), amlodipine (Norvasc) and others.
People who suffer from kidney disease or kidney failure should not take magnesium glycerophosphate or any other magnesium supplements. Magnesium is not filtered properly by damaged kidneys, and taking extra amounts of the mineral can raise magnesium to harmful levels.
Heart block is a cardiovascular condition that affects the heartbeat and occurs when the electrical signal between the top and bottom chambers of the heart is impaired. Large doses of magnesium should not be given to people diagnosed with heart block as it can cause severe muscle weakness and worsen the condition.