The "best" cough medicine is ultimately based on the ... It is most commonly sold as a syrup but can be found as capsules and lozenges. Dextromethorphan is the active ingredient in single-symptom ...

It acts centrally and elevates the threshold for coughing. It is about equal to codeine in depressing the cough reflex. In therapeutic dosage dextromethorphan does not inhibit ciliary activity.