Were you at a regular doctors office or the ob/gyn? If you weren't at the ob/gyn I'd be a little skeptical of taking the med.
I am surprised they would give you anything with one high blood pressure
reading. The high BP
with pre-eclampsia is usually noted after 24 weeks and could mean other things if noticed before 24 weeks.
I'd just keep a close eye on the BP, and if it still runs high constantly talk with your ob/gyn about any kind of meds.
I usually don't tell anyone to quit taking medication, but if it was a primary care
doctor I would honestly talk to the ob/gyn before continuing it.