Mucinex acts as a mucus thinner, which makes postnasal drip less uncomfortable and less likely to lead to a secondary infection, according to WebMD. However, the most effective method of treating postnasal drip depends on whether the cause is allergies or a bacterial or viral infection.
There are steroid medications and nasal sprays that are also effective against allergy-induced postnasal drip, says WebMD. Medication alternatives to Mucinex for postnasal drip caused by infection include antihistamines and decongestants.
Other methods for thinning mucus are drinking more water, using saline nasal sprays or rinses to flush out the sinuses, and using a vaporizer or humidifier, according to WebMD.