My dear young man,
Welcome to Health Care Magic
It is a symptomatic treatment / not disease modifying drug.
Usually, the doctor will step up to maximal dose / if not improved, add another drug acting by a different mechanism (example: Flotral-D)
The drug helps the physiological part of obstruction...it is mostly mechanical obstruction and needs mechanical relief - surgery.
You will have to take it for life time or till surgery (prostatectomy
Wishing speedy recovery