Can an asthma patient take magnesium oxide 500 mg? Is the magnesium oxide 500mg beneficial in asthma conditions? I am suffering from the asthma from quite some time now but I am at a stable condition at this point of time. I want to take the magnesium oxide 500 mg. Should I do so, can it be harmful in any way? Would you advise it in my condition? What are your opinions about my situation?