When I Was First Put On Atenolol About 2 Years

When I was first put on atenolol about 2 years ago for high blood pressure my doc put me on 50mg and told me to take one every morning. I felt awful all day.....lightheaded, dizzy, sleepy, and almost passed out a couple of times. So, my doc reduced my dosage to 25mg and suggested that i take it in the evening instead. Since then, I notice that I don't sleep well at all. When is the best time of day to take atenolol.....morning or evening? Do you think my body has adjusted to atenolol enough that maybe it is better for me to take it in the morning instead?? Also, Is it true that it depletes melatonin and CoQ10 from the body??