Check with the chemist but I'm 99% sure it won't do any harm.

Drinking lots of water is just as good (the idea is to flush out the system) but if any of the other women have had it they'll tell you to get some Ural and if you've already got some sachets, it looks more convincing iykwim.

You'll have to claim it's a pretty bad case though to be lasting two days. Just talk it up big time. Say you've had it before but it's never been this bad etc.

Like I say, once you mention anything to with urinary tract infections, most people stop listening so it's a good cover story! Not that I've ever used it as a sickie excuse or anything!