Should you take ephedrine and pseudoephedrine together?

I know one is man-made & they have a slightly different chemical make-up, but what I want to know is should you take them together? Say you have allergies and already take something like Allegra D every day that has pseudoephedrine in it, but you get a cold or sinus infection. Can you take a medicine with ephedrine that says to take every 4-6hours as needed for your acute problem and continue taking your daily allergy medication that has the pseudoephedrine? If it's ok, is that just for someone who is generally healthy? What if you have COPD? What if you are a Diabetic? What other conditions should you be aware of if taking either of these medications, alone or together for an acute problem? Thanks for any help!