I believe it is best to talk to a doc or pdoc about this, I am sure this med is for allergies, but some may find the use for sedation or semi-sedation.
Long term effects I would say one can build up tolerance to it, so it is best to take this up with a doc. If you are using it for allergies and haven't gotten any relief, I'd see an ENT for an allergy evaluation (I did) to pin point the exact thing you are allergic to, then take meds as prescribed.
Just my take on this.

DE

In giving advice seek to help, not please your friend
SOLON