Doesn't it depend on the type of Diltiazem, whether it's slow release or not? I take the slow release type, once a day. I thought I read the half life is about 16 hours. When I went off of my med, it took 3 days before my chest pains came back.
In either case, I'd say (msanxiety) that the med is out of your system by now.
The average time it takes to leave the body is 8 hours. If you think you are still having side effects from it, you're not. Probably just anxiety.