Was Taking Four 6.25 Doses Of Coreg Six Hours Apart.

Was taking four 6.25 doses of Coreg six hours apart. Doctor now wants to change to 20 mg Coreg CR TWICE a day. I have many serious problems with hypertensive RXs but have been able to tolerate Coreg. Also take 3 doses daily of Vasotec; 10 mg morning, 10 mg. mid-day and 20 mg at night. I Understand about the differences in dosing, but very worried about 2 doses. Have taken 3 days of morning (only) dose......feeling the effects somewhat. Am trying to establish safety overall, and how safe w/Vasotec too??