The present invention relates to pharmaceutical compositions comprising dextromethorphan or a physiologically acceptable salt thereof, quercetin, resveratrol, and hesperidin. The invention further relates to nutraceutical or dietary supplement composition comprising a physiologically acceptable salt of magnesium, quercetin, resveratrol, and hesperidin. Further provided are methods for treating respiratory disease in a human subject by substantially eliminating phlegm from the lung through administering to the subject effective amounts of compositions of the invention.
