how long before BP goes down?

I started Lisinopril about 10 days ago. What time frame do you have to be taking it before your BP goes down? I had it checked a couple of days ago at another doctors appt and it was still high. No side effects other than when I wake up in the middle of the night I feel like my throat is swollen or has a lot of mucus in it but there is no cough and it is not scratchy either. I have never had high BP before until this last year after I had been taking Prempro hormone replacement. My regular doctor thinks that this might be what is causing it. Anyone else have this issue before? Thanks....