<p>Other medicines can affect treatment with Magnesium Oxide tablet. If you are using any of the following: medicines, tell your doctor; muscle relaxants (non-depolarizing neuromuscular blockers), aminoquinolones, nitrofurantoin, penicillamine, tetracyclines, fluoroquinolones (antibiotics), Digoxin (for the treatment of heart failure), Lithium (Control of emotional changes and depression), Sodium polystyrene sulfonate (allows potassium to be removed from the body), Cellulose sodium phosphate (used to prevent kidney stones), Other medicines containing magnesium (including magnesium enemas), Barbiturates (drugs used for the treatment of insomnia), opioids (substances that act as morphine in the body), hypnotics (soporific), Nifedipine (drugs used in high blood pressure or heart problems).</p>