Treatment for a runny nose is entirely dependant on the cause and may include antibiotics, antihistamines or decongestants, states WebMD. If the cause of post-nasal drip is a bacterial infection, the best treatment is antibiotics. For a runny nose caused by a viral infection or sinusitis, antibiotics won't help.
New types of antihistamines are very effective but have a wide range of side effects, according to WebMD. It is best to speak with a doctor about post-nasal drip before using antihistamines. A simple treatment that may help is using a humidifier or vaporizer to increase the moisture content in the air. Saline nasal spray and a medication like Mucinex may also help treat a runny nose.