Preeclampsia is NOT just hypertension, but also added with protein in the urine, etc. There are more signs then just hypertension. Also, just so you know, 98% of BP issues are due to the kidneys and during the end of the pregnancy, your kidneys are flitering your body with the added pressure of your baby.
Depending on how life threatening your BP is, you may want to consider doing something else to HELP your kidneys rather than adding medication that your kidneys have to process, as well. If you had Pitocin, an epidural, and an IV, then your kidneys are still dealing with those meds as well.
Maybe start with CranActin (you should be able to find it locally) or PURE cranberry juice - like 2-3 oz per day WITHOUT any sugar AND preferably NOT from concentrate. Add distilled water for ONE day to flush them out. Try the cranberry and 3-4 liters of waters for a week and see if that brings it down. Eat salt/sodium minimally and I bet you'll see a turnaround!
Good luck!