I'm on toprol (metoprolol) xl for tachycardia & high bld press. i have an epipen incase of allergic reactions. is it safe to use if i get a reaction or no?

Yes: Epinephrine is the only effective drug for the treatment of anaphylaxis. While it can cause arrhythmias in susceptible individuals, the medication is probably safer than untreated anaphylaxis. There are many causes of anaphylaxis, some of which are treatable, such as bee sting allergy. You should consult with an allergist.

Epi Pen: The epi pen is to be used for a severe, often life threatening, allergic reactions. In that situation blood pressure is often dangerously low so the epi pen is beneficial. When used in the proper situation, an epi pen would be safe and even beneficial.