Tamsulosin is okay. I would self ground for a week just to make sure you haven't got any side effects.
If you are certified at the level of CFI, you should inform your AME. Then skip to the last paragraph.
If you are certified below that level, you've never read part 67 and you are goverened by 61.53, "what a reasonable pilot would do".
At the end of the week, I would obtain the letter from the urologist in any case (visit the nurse, get her to write, sing doc's name with her initials after the signature or however that office does that), that you are taking the med without side effects, and file it away for your next 8500-8 encounter.
http://www.faa.gov/library/reports/medical/fasmb/media/201101_color.pdf
Think of Tamsulosin as yet another antihypertensive. You can tell in a week. Tamsulosin escaped this round of specifications, see the bottom of page 3.