What Is The Difference Between Norvasc And Losartan For High

What is the difference between Norvasc and Losartan for high blood pressure? I am currently taking Norvasc and my bp drops dramatically (from 150s/70s or 80s to 100-107/upper 60s) about an hour after I wake up in the morning and I can't stay awake. After it hits its low it comes back up after 1 1/2 or 2 hours and I can function again. Could it be the Norvasc causing the drop? I have altered when I take it - from 11pm to 5 or 6pm, hoping to change the time of the drop but it hasn't made a difference.