Have you already picked up the prescription, because if so, look at the leaflet, they should enclose one.
I have no experiances with this med. I would say, in general, anti-depressants are unlikely to cause weight gain, its older antipsychotics that are notorious for that.
Bearing in mind the internet is not always accurate, maybe have a look for a factsheet on this drug.
Remember the theraputic dosage may sound a lot, but what is theraputically useful varies so much from drug to drug.
xx
edit: this link may be of use..
http://www.patient.co.uk/showdoc/30002347/