Hi Celena,
Since lodrane24 is an antihistamine it will dry up all your secretions, including CM. It appears to be just for symptom control more than anything, not a curative measure (although if she is concerned you could develop an ear infection from the fluid in your ears she may be considering that as preventative).
I would think it would just be a judgment call for you, whether you are suffering enough that you need to take the medication during o time, or whether or not it can be managed with a netti pot or other alternative measures.
Best of luck with whatever you decide!
ETA that it is a catagory C drug meaning no controlled studies have been done on pregnant women and what little info seems to be available shows it is linked with increased risk of congenital defects in the baby if used in early pregnancy:
SafeFetus.com