Can i take zyrtec in the morning and benadryl (diphenhydramine) at night for postnasal drip? need relief in the morning. going to ent in december.

Yes: Should not be a problem and is done by many.

Yes: Postnasal drip: Every day, glands in the linings of your nose make about a quart of mucus each day. The excess can come out of the nostrils -- that’s a runny nose. When the mucus runs down the back of your nose to your throat, it's called postnasal drip. http://www.webmd.com/allergies/postnasal-drip