topical decongestant topical decongestant topical decongestants are decongestants applied directly to the nasal cavity. their effectiveness by themselves in the common cold appears to have a small benefit in adults. topical decongestants should only be used by patients for a maximum of 5–7 days in a row, because rebound congestion may occur in the form of rhinitis medicamentosa. when used in adults for a short period of time side effects appear to be few. mechanism of action topical decongestants are vasoconstrictors, and work by constricting the blood vessels within the nasal cavity. examples ephedrine levomethamphetamine naphazoline oxymetazoline phenylephrine pseudoephedrine tramazoline xylometazoline