I Was Taking Metoprolol Succ 100 Mg. Once Daily But

I was taking Metoprolol Succ 100 mg. once daily but it was too strong. The Dr. now has prescribed Metoprolol Tartrate 50 mg. once a day. He also chanaged my Amlodipine Besylate from 10 mg. to 5 mg. once daily. Along with this I am taking Clopidogrel Bisulfate 75 mg. once daily. I have had two TIAs.
He changed the dosages because my b/p was very low and I passed out.