Diltiazem 120mg/24 ER (Extended Released)

I am currently taking Lisinopril 20mg in the 7:30AM and Diltiazem 120mg/24 in the 4:30PM.
My doctor asked me to take both medications in AM so that it works all day.
I thought Diltiazem is a slow-releasing 24hours drug.
As long as I continue to take it at the same time each day,
I will have it in my bloodstream continuously.  

Does it matter when to take it?

[ireneo]

When I took Diltiazem, I took it at night to avoid some of the initial side effects: headache, fatigue, a bit of dizziness. Once those little irritations passed, I just continued taking it at bedtime because that was my routine. But you're right, once your body is up to the therapeutic dose circulating through your body, the main thing is to be consistent about the time you take it.