How can I get rid of post nasal drip completely?

Intranasal steroids. In addition to using a neti pot, antihistamines (like zyrtek, Allegra and claritin), intranasal steroids (like Nasonex (mometasone) and flonase) prescribed by your doctor can work very well to relieve post nasal drip. The intranasal steroids take a few days to kick in, so don't expect to get a lot of relief right away.