i have a 12lb 3 month old puppy. I didnt want to give him peroxide so i gave him half a tbsp of robbitusin DM. every 9 hrs or so. After only 2 dys he stopped coughing . I also applied honey mixed with a little lemon juice directly in his mouth everytime he started coughing too much.
EC: More info about Robitussin DM here: http://www.petplace.com/drug-library/dextromethorphan-robitussin-dm/page1.aspx