What is the indication for the use of magnesium in cardiac arrest?

If there is suspected hypomagnesemia present that’s the time that you can use the magnesium. This is for use in cardiac arrest.  This kind of drug is life threatening ventricular arrhythmias due to digitalis toxicity. There is insufficient evidence to recommend for or against the routine administration of magnesium during cardiac arrest. Magnesium is for the treatment of documented hypomagnesemia or for torsade de pointes.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: