The most effective medicine for a runny nose due to a common cold is an antihistamine (such as chlorphenamine), as it helps reduce sneezing and nasal discharge. You can also use a simple saline nasal spray to gently rinse and clear the nasal passages, or steam inhalation to thin the mucus. If congestion is troublesome, a short course of a decongestant (such as phenylephrine) and a mucolytic (such as ambroxol) may help. Always check labels to avoid taking two medicines that contain the same active ingredients.